Additive Effects on Asymmetric Catalysis - Chemical Reviews (ACS

Review pubs.acs.org/CR

Additive Effects on Asymmetric Catalysis Liang Hong,† Wangsheng Sun,‡ Dongxu Yang,‡ Guofeng Li,‡ and Rui Wang*,†,‡ †

School of Pharmaceutical Sciences, Sun Yat-sen University, Guangzhou, 510006 China Key Laboratory of Preclinical Study for New Drugs of Gansu Province, Lanzhou University, Lanzhou, 730000 China

‡

ABSTRACT: This review highlights a number of additives that can be used to make asymmetric reactions perfect. Without changing other reaction conditions, simply adding additives can lead to improved asymmetric catalysis, such as reduced reaction time, improved yield, or/and increased selectivity.

CONTENTS 1. Introduction 2. Mechanistic Role 3. Additive Effects on Organocatalytic Asymmetric Reactions 3.1. Acids in Organocatalytic Asymmetric Reactions 3.1.1. Inorganic Acids and Carboxylic Acids 3.1.2. Amino Acids 3.1.3. Sulfonic Acids 3.1.4. Phosphoric Acids 3.2. Amines in Organocatalytic Asymmetric Reactions 3.2.1. Et3N or iPr2NEt 3.2.2. Pyridines 3.2.3. DMAP 3.2.4. Imidazoles 3.2.5. DABCO and DBU 3.2.6. Guanidines 3.2.7. Proton Sponge 3.2.8. Pyridinone 3.3. Salts in Organocatalytic Asymmetric Reactions 3.3.1. Lithium Salts 3.3.2. Sodium Salts 3.3.3. Potassium Salts 3.3.4. Magnesium Salts 3.3.5. Ti(OiPr)4 3.3.6. Other Salts 3.4. Alcohols and Phenols 3.4.1. Alcohols 3.4.2. Phenols 3.5. Molecular Sieves in Organocatalytic Asymmetric Reactions 3.5.1. Three Angstrom MS 3.5.2. Four Angstrom MS 3.5.3. Five Angstrom MS 3.6. Water in Organocatalytic Asymmetric Reactions

© 2016 American Chemical Society

3.7. Thiourea in Organocatalytic Asymmetric Reactions 3.8. Others 3.8.1. Amberlite CG50 3.8.2. BBr3 3.8.3. (Boc)2O 3.8.4. Bromine Salt 3.8.5. Cl3CCN 3.8.6. 18-Crown-6 3.8.7. HOAt or HOBt 3.8.8. Oxime 3.8.9. Silica Gel 3.8.10. Trialkyl Phosphite 3.8.11. TMSCl or TMSOH 3.8.12. Vinyl Ethyl Ether 4. Additive Effects on Metal-Catalyzed Asymmetric Reactions 4.1. Acids in Metal-Catalyzed Asymmetric Reactions 4.1.1. Carboxylic Acids 4.1.2. Chiral Acids 4.1.3. Sulfonic Acids 4.1.4. Phosphoric Acids 4.1.5. Inorganic Acids 4.2. Amines in Metal-Catalyzed Asymmetric Reactions 4.2.1. Et3N 4.2.2. Pyridines 4.2.3. DBU, DABCO, or NMI 4.2.4. Chiral Amines 4.3. Salts in Metal-Catalyzed Asymmetric Reactions 4.3.1. Lithium Salts 4.3.2. Sodium Salts 4.3.3. Potassium Salts 4.3.4. Cesium Salts 4.3.5. Silver Salts

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Received: November 17, 2015 Published: February 16, 2016 4006

DOI: 10.1021/acs.chemrev.5b00676 Chem. Rev. 2016, 116, 4006−4123

Chemical Reviews 4.3.6. Ammonium Salts 4.3.7. Other Salts 4.4. Alcohols and Phenols in Metal-Catalyzed Asymmetric Reactions 4.4.1. Alcohols 4.4.2. Phenols 4.5. Phosphanes, Phosphane Oxides or Phosphoramidates 4.5.1. Phosphanes 4.5.2. Phosphane Oxides 4.5.3. Phosphoramidates 4.6. Halides in Metal-Catalyzed Asymmetric Reactions 4.7. Others 4.7.1. Aldehydes 4.7.2. Amino Alcohols 4.7.3. B(OMe)3 or BPh3 4.7.4. (Boc)2O 4.7.5. Cobalt Complex 4.7.6. Crown Ethers 4.7.7. Dibenzylideneacetone 4.7.8. Methyl Benzoate 4.7.9. Styrene 4.7.10. TMSCl 4.7.11. Water 4. Summary and Outlook Author Information Corresponding Author Notes Biographies Acknowledgments References

Review

strategy has been applied in various transformations with high efficiency. Both its improved practical efficiency and enhanced aesthetic appeal provide organic chemists with a prodigious starting point to discover a new strategy for methodology development. Surprisingly, there has been no recent attempt to overview the development of this particular field in the past decade, apart from a monumental review by Shibasaki in 1999 on the additives and cocatalysts for perfect asymmetric catalysis.1 However, this review only covered a limited amount of literature and was not updated for a long time. With the explosive development of asymmetric catalysis, especially asymmetric organocatalysis since 2000, considerable reactions in which additives were used to improve the efficiency have been developed. In this review, we will present a systematic summary on the development of additives. It will cover recent efforts and advances during the last decade in the application of additives in various transformations, including metal-catalyzed asymmetric reactions and organocatalytic asymmetric reactions. Due to there being too much literature in this area, for example, in almost all amine-catalyzed reactions, acid additives were used to accelerate the reaction, we therefore only discuss some representative examples.

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2. MECHANISTIC ROLE Introduction of an additive may help to optimize or even greatly improve asymmetric reactions as they are often sensitive to slight changes in reaction conditions. In general, the main object of introducing an additive is to activate substrates, promote the formation of a transition state, modify the structure of catalyst or transition state, protect or regenerate the catalyst, or block the side reaction. However, it’s hard to predict which additive may be beneficial for one reaction, as it was usually found by chance or by random screening, and one kind of additive may have a different or even opposite effect. Furthermore, for the same additive, it may have different functions for different reactions, and sometimes several different kinds of additives are beneficial for the same reaction. In addition, compared to the mechanistic study of a reaction, the mechanistic role of an additive is far less studied. Thus, the mechanistic role of an additive is complicated, and it is hard to summarize a general mechanism for an additive, some of which can only be elucidated after mechanistic studies. In this review, wherever possible, a mechanistic discussion on the influence of an additive will be discussed in detail in the corresponding reaction where a general mechanistic role of an additive is stated in original papers.

1. INTRODUCTION The development of efficient asymmetric catalytic systems for valuable organic transformations has always been one of the pursuits of organic chemists. How to make an asymmetric reaction perfect has therefore been a main concern, and tremendous efforts have been devoted to it by synthetic chemists.1 Among various strategies, the introduction of a suitable additive to a specific catalytic system, which in many cases enhances the reactivity or/and the selectivity2 (including chemo-, regio-, diastereo-, and enantioselectivity) dramatically or sometimes magically modifies the reaction pathway, has emerged as a powerful and exciting tool for the construction of various molecules with the control of regio-, diastereo-, and enantioselectivity (Figure 1). For a simple example, addition of water usually accelerates the proline-catalyzed aldol reactions with improved yields and enantioselectivities.3−6 During the last decade, great success has been achieved in this area and the

3. ADDITIVE EFFECTS ON ORGANOCATALYTIC ASYMMETRIC REACTIONS 3.1. Acids in Organocatalytic Asymmetric Reactions

3.1.1. Inorganic Acids and Carboxylic Acids. After discovery of the Hajos−Parrish−Eder−Sauer−Wiechert reaction, in the next 30 years there have been only limited and less noticed examples concerning chiral amino acids-mediated asymmetric reactions; moreover, regarding chiral amine salts, there seems like there has been no important development. Since 2000, amine-catalyzed asymmetric reactions via iminium ion7 or enamine8 activation have undergone explosive development, in which the selectivity was usually controlled by the structure of chiral amines (Scheme 1). In most cases, the acid additives are essential, as they could accelerate the formation of

Figure 1. Improved efficiency caused by additive. 4007


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Scheme 1. General Acid Effects on Amine Catalysis

Scheme 2. Diels−Alder Reaction10

Table 1. [3 + 2] Cycloaddition Reaction11

entry

HX

t (h)

yield (%)

exo:endo

ee (%) (exo)

1 2 3 4 5

HCl HOTf TFA HBr HClO4

108 101 80 80 80

70 88 65 77 86

88:12 89:11 72:28 94:6 94:6

95 90 86 93 90

iminium ion or enamine intermediate, activate substrate, or assist the release of the product. Later, it was found that the chiral anions sometimes could also affect the stereocontrol, which had been defined as asymmetric counterion-directed catalysis (ACDC).9 In 2000, MacMillan and co-workers firstly disclosed that chiral amine salts could act as powerful organocatalysts in mediating highly enantioselective Diels−Alder reaction and proposed that the reversible formation of iminium ions from α,β-unsaturated aldehydes and amine salts might emulate the equilibrium dynamics and π-orbital electronics that are inherent to Lewis acid catalysis (Scheme 2).10 In their later studies of chiral amine salts in the asymmetric [3 + 2] cycloaddition reaction it was found that the Brønsted acids additives had obvious effects on influencing the results of the reaction’s reactivity, diastereoselectivity, and enantioselectivity (Table 1).11

Then the MacMillan group demonstrated that this organocatalytic strategy was also amenable to the enantioselective Friedel−Crafts alkylation of pyrroles with α,β-unsaturated aldehydes to generate β-pyrrolyl carbonyls (Table 2).12 In this work, it is shown that the stronger acid additive would remarkably increase the reactivity of the addition process; the amine/TFA salt showed the best catalytic ability as the reaction could be finished in shorter times and resulted in higher yields. Thus, in this process the acid additives might be helpful in promoting the formation of iminium ion and the anion of the acid might also have obvious effects on influencing the reactivity of the LUMO transition state in the iminium ion pair. The corresponding X-ray crystal diffraction analysis of the iminium ion pair intermediate generated from α,β-unsaturated aldehydes and Macmillan’s catalyst was studied by Sparr and Gilmour (Scheme 3).13 The iminium ion pair intermediate could be obtained smoothly under mild conditions and proved 4008


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Table 2. Friedel−Crafts Alkylation12

entry

HX

t (h)

yield (%)

ee (%)

1 2 3 4

NCCH2CO2H Cl2CHCO2H Cl3CCO2H CF3CO2H

32 32 3 3

10 62 64 78

80 80 81 81

4, the cyclopropyl iminium ion could be easily prepared from the cyclopropane carbaldehyde and MacMillan’s catalyst in the presence of hexafluoroantimonic acid and analyzed by X-ray crystallographic studies. The internuclear distance of the cyclopropane ring was altered after the formation of the iminium ion pair, which would cause the symmetry of the cyclopropane ring to be broken, and resulted in higher reactivity. After the optimization progress, introduction of TFA as a cocatalyst into the reaction would lead to better results. In some cases, the Brønsted acid additives could activate the electrophiles by an ion pair.15 Cozzi and Tian et al. disclosed the acid coadditive played a crucial role in the amine-mediated direct asymmetric alkylation of aldehydes.16,17 They found that introduction of different acid coadditive into the same amine catalyst would result in dramatically changed enantioselectivities. The authors inferred that the acid additives in the catalytic cycle might be responsible for generation of the carbocation by formation of an ion pair (Scheme 5).16 In the case of an asymmetric aldol reaction of cycloketones with aldehydes, the switch of diastereoselectivity could be realized by the use of acid additives, which featured a long carbon chain or a hydrogen-bond donor.18 The combination of chiral amine with TFA preferred the formation of anti product with a syn:anti ratio of 14:86. However, the main syn product could be obtained when adding an acid with a long carbon chain. Subsequent screaming revealed that the introduction of a carboxyl group was more effective. The use of succinic acid afforded the product with a syn:anti ratio of 75:25. The diastereoselectivity might be affected by the steric hindrance between the cyclohexene ring and the R group of aldehyde. Thus, the introduction of a bulky anion group or a hydrogenbond donor may push the R group of the aldehyde to the other side (Scheme 6). The acid additives could also induce the switch of enantioselectivity. In 2012, Maruoka and co-workers found that the C6F5CO2H additive could lead to the reversion of enantioselectivity in the diamine-catalyzed asymmetric aldol reaction of ketones and α-ketoesters (Table 3).19 Chiral diamine without the combination of acid could efficiently catalyze the reaction to afford the product in high enantioselectivity with (R,R)-configuration. Interestingly, addition of C6F5CO2H reversed the configuration to (S,S). Further increasing the amount of additive led to the improvement of diastereoselectivity but reduced the enantioselectivity. Using

Scheme 3. X-ray of Iminium Ion Intermediate13

by X-ray crystallographic analysis. The model reaction between iminium ion intermediate and pyrrole proceeded smoothly and generated the relative conjugate adduct in similar results under slightly different reaction conditions. The iminium ion activation model can be applied to the activation of not only α,β-unsaturated aldehydes but also cyclopropane carbaldehydes. In 2011, Sparr and Gilmour reported an important piece of work on the study of cyclopropyl iminium ion intermediate.14 As shown in Scheme Scheme 4. Activation of Cyclopropane Carbaldehyde14

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Scheme 5. Alkylation of Aldehyde16

Scheme 6. Aldol Reaction of Cycloketone with Aldehyde18

water instead of CH3OH could also reverse the enantioselectivity. On the basis of the DFT calculations, they proposed two activation models: (1) without an additive, the α-ketoester was activated by the interaction of a hydrogen bond between its carbonyl group and the hydrogen atom of acidic Tf-amide and

enamine; (2) in the presence of acid additive and water, which was generated from the formation of enamine, the hydrogen atom of Tf-amide interacts with the carbonyl group while the hydrogen atom of enamine recruits the acid additive. 4010


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Table 3. Aldol Reaction of Ketone and α-Ketoester19

entry

solvent

1 2 3 4 5

MeOH MeOH MeOH MeOH H2O

x

yield

syn:anti

ee (%)

1 3 10

63 71 37 32 47

8.1:1 9.2:1 13:1 13:1 6:1

+94 −42 −58 −60 −58

Scheme 7. Mannich Reaction of Ketone and Cyclic Imino Ester19

Scheme 8. Michael-Aldol Domino Reaction of Thiol with Enal20

The same author found a similar reversal of enantioselectivity in the asymmetric Mannich reaction of ketones and cyclic

imino esters (Scheme 7). Different from the aldol reaction mentioned above, the use of pentafluorobenzoic acid 4011


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Scheme 9. γ-Amination of Enal21

Scheme 10. Vinylogous Michael Addition25

However, when using a base like NaHCO3 instead of PhCO2H, the tetrahydrothiophene methanone was obtained in 61% yield and 80% ee. It should be noted that though the yield was moderate, only a single regio- and diastereomer was obtained. The reason for this difference was that the intermediate I had a different fate under acidic or basic conditions. In NaHCO3, the hydrolysis of the intermediate I released the catalyst and the Michael product, which underwent a diastereospecific aldol reaction to give tetrahydrothiophene methanone. In this case,

C6F5CO2H was unable to reverse the enantioselectivity while the use of 2,6-dinitrobenzoic acid could switch the configuration.19 In the asymmetric Michael-aldol domino reaction of thiols with enals, Jørgensen and co-workers found an interesting phenomenon that the regioselectivity of this reaction could be controlled by the appropriate choice of additives (Scheme 8).20 In the presence of PhCO2H, the reaction afforded the tetrahydrothiophene carbaldehyde in 56% yield and 94% ee. 4012


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Scheme 11. Diels−Alder Reaction.28

addition of NaHCO3 could promote the hydrolysis and enolization. In PhCO2H, the intermediate I was not hydrolyzed and involved in the subsequent aldol reaction to generate the intermediate II, whose hydrolysis afforded the tetrahydrothiophene carbaldehyde. The acid additives were beneficial for the dienamine catalysis.21−24 For example, in the asymmetric γ-amination of α,β-unsaturated aldehydes,21 although an excellent enantioselectivity of 97% ee was observed in the absence of an additive, the yield was only 21%. However, after addition of benzoic acid, the yield could be improved to 46% without any loss of enantioselectivity (Scheme 9). About the mechanism, the acid additive could promote the reaction between the catalyst and the aldehyde to generate the iminium-ion intermediate, which could then form the dienamine intermediate by the deprotonation. By using a similar dienamine activation strategy, Melchiorre et al. realized the asymmetric vinylogous Michael addition of cyclic enones to nitroalkenes (Scheme 10).25 They found the acid additives were crucial for the reaction as almost no reaction occurred using a stronger acid like CF3CO2H, and using 2FPhCO2H gave the best results of >95% conversion and 82% ee. Fine tuning the acid additive was essential to modulate the delicate equilibrium between the iminium ion and the crossconjugated and extended dienamine intermediates. Jørgensen et al. found that with the assistance of an acid additive, secondary amines and polyenals could generate reactive trienamine intermediates, which could readily participate in many reactions.26,27 By mixing dienal and amine in a 1:1 ratio without an acid, less than 10% of trienamine was observed after 1 h; however, on addition of 0.5 equiv of acid additive, the observed catalyst incorporation reached 50%. For the trienamine-catalyzed Diels−Alder reaction with 3-olefinic oxindoles, the combination of amine with 2-fluorobenzoic acid gave the best results of 91% yield and 98% ee, while the use of a weaker benzoic acid led to a lower yield with a significantly longer reaction time, and stronger 3,5-bis(trifluoromethyl)benzoic acid resulted in a slight loss of yield and enantioselectivity (Scheme 11).28 Other dienophiles, such as olefinic cyanoacetates,28 thiocarbonyls,29 or chromones,30 could be applied in this [4 + 2] cycloaddition. The same group further extended this linear trienamine catalysis to the cross-conjugated trienamine catalysis using cyclic dienal. For the Diels−Alder reaction with 3-olefinic oxindoles, addition of acid additive was necessary for high conversion (Scheme 12). In the absence of an additive, moderate conversion was obtained. Addition of acids greatly improved the conversion to >95%. However, the enantioselectivity seemed to correlate with the acidity of the additives, as the difference of enantioselectivity was significant when using different acids. The best results were obtained with the use of 2fluoro- or nitrobenzoic acid, giving the product in full conversion and 97% ee.31 Similarly, using the same trienamine strategy, Chen and coworkers developed some [4 + 2] cycloaddition of 2,4-dienals or 2,4-dienones with 2,4-dienes,32 nitroalkenes,33 maleimide,34,35 methiodide salts,36 or 1-aza-1,3-butadienes.37 In addition to 2,4dienals or 2,4-dienones, they also found the trienamine strategy can be extended to 2,5-dienones for the remote δ,ε-CC bond activation.38 In the model reaction of 2,5-dienone with 1azadiene, the acid additives had significant effects on the reaction. 2-Hydroxybenzoic acid gave the best results of 92% yield and >99.5% ee, while 3-hydroxybenzoic acid led to poor

reactivity of 95% when Et3N was added to the reaction. Et3N was proposed to function as a Brønsted base to activate the allylidenemalononitriles by a remote deprotonation process. Hong and co-workers accomplished a tandem reaction between poly-nitro group compounds and two molecules of α,β-unsaturated aldehydes (Scheme 32).71 The optimization process showed that the Brønsted base played an important role in promoting the reaction by assisting the deprotonation of the ε-site of the (E)-2-methyl-1,5-dinitro-3-(2-nitrovinyl)benzene. Notably, with strong bases, such as DBU and DABCO, the reactions are readily reversible with quantitative recovery of the starting materials and polar residues. The best results of 54% yield and >99% ee were obtained in the presence of iPr2EtN in toluene. The reaction could access a series of enantioenriched and highly functionalized hexahydrophenanthrenes containing five multiple stereogenic centers with excellent diastereo- and enantioselectivities. The Brønsted base additive could also effectively promote the reaction by a deprotonation process of nucleophiles (Scheme 33). In 2005, the Jacobsen group realized the asymmetric aza-Henry reaction of a series of nitroalkanes and

Scheme 31. Domino Reaction between Allylidenemalononitrile and Enal70

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Scheme 32. Synthesis of Hexahydrophenanthrene71

Scheme 33. Aza-Henry Reaction72

The same group also utilized this strategy to access a series of tricyclic β-lactones from keto acids via an unsymmetric process (Scheme 39).80 However, the asymmetric cyclization of keto acid needed the use of stoichiometric quantities of commercially available (S)-tetramisole hydrochloride, affording the tricyclic product in moderate yield with excellent enantioselectivity. Notably, the reaction also needs stoichiometric quantities of iPr2NEt to in-situ generate the nucleophilic catalyst and promote the reaction pathways by assisting the deprotonation process. Importantly, this work provided the first direct evidence for nucleophile involvement in the stereodefining step of biscyclizations with keto acid substrates and the first demonstration of isothioureas in ammonium enolate chemistry. In 2010, Romo’s group extended this approach to the catalytic asymmetric aldol-lactonization of keto acids using Birman’s homobenzotetramisole derivative as a chiral catalyst (Scheme 40).81 The reaction also needed 4.0 equiv of iPr2NEt

(Scheme 38).79 In this work, they chose iPr2NEt as a powerful Brønsted base to promote the reaction pathway: (1) initial derivatization of carboxylic acid to activated ester with Mukaiyama’s reagent needed the Brønsted base to neutralize the chlorine hydride; (2) the deprotonation process to generate the activated acyl ammonium needed the Brønsted bases’ function. In other words, the activated acyl ammonium might be generated through ketene, which could be formed directly via an elimination reaction in the presence of iPr2NEt. Scheme 34. [3 + 2] Cycloaddition73

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Scheme 35. Kinetic Resolution of Secondary Alcohol74

Scheme 36. Dearomatization of Alkylated Isoquinoline75

Scheme 37. Substitution of 3-Bromooxindole76

Scheme 38. Aldol-Lactonization Reaction79

to promote the cyclic reaction and neutralize the chlorine hydride generated from the substrate and the activating reagent TsCl. Notably, the optimization process in this work demonstrated the use of inexpensive TsCl instead of Mukaiyama’s reagent as an activating reagent to provide the products in excellent enantioselectivities and good to excellent yields. Subsequently, they utilized this catalytic asymmetric reaction as the key step in the asymmetric total synthesis of (−)-curcumanolide A and (−)-curcumalactone.82

On the basis of the pioneering work on application of carboxylic acid-derived ammonium enolates in asymmetric intramolecular aldol reaction processes, the first intramolecular Michael reaction using this strategy was realized by Smith’s group for the first time in 2011 (Scheme 41).83 The reaction employed (S)-tetramisole hydrochloride as a nucleophilic 4022


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Scheme 39. Synthesis of Tricyclic β-Lactone80

Scheme 42. Synthesis of δ-Lactones90,91

Scheme 40. Aldol-Lactonization of Keto Acid81 ion by using a chiral thiourea and 2,6-lutidine catalyst system (Scheme 44).94 This methodology provided efficient access to obtain enantioenriched tetrahydro-β-carbolines with excellent enantioselectivities. Moreover, the imines could be in-situ generated by condensation of tryptamine with aldehydes, and the yields of the cyclization products for the two-step procedure were generally good. The Akiyama group found that phosphoric acid pyridinium salt could exhibit efficient catalytic activity in the aza-Diels− Alder reaction between Brassard’s dienes and imines (Scheme 45).95 Introduction of pyridine into the catalyst system could in-situ generate the combinational catalyst which could change the stereocontrolled environment of phosphoric acids. This method afforded a series of chiral piperidinone derivatives in high yields and with excellent enantioselectivities. The Ishihara group also designed an elegant combinational catalyst system which consisted of a chiral disulfonic acid and a pyridine.96 The author evaluated different bases effect on the combinational catalyst in the Mannich-type reaction between pentanedione and Cbz-imine (Scheme 46). In the optimization process, a series of pyridine derivatives was screened. It was found that pyridine, 2-phenylpyridine, and 2,6-lutidine gave the Mannich product in low yield due to the insolubility of the corresponding salts. In sharp contrast, the introduction of 2,6di-tert-butylpyridine could improve the enantioselectivity to 76% ee. The use of 2,6-diphenylpyridine would lead to further improvement of ee to 92%. By analyzing these results it was speculated that the combinational catalyst’s Brønsted acidity and bulkiness effect could be regulated by rational selection of the coordination partners. The Ooi group also demonstrated that the introduction of 2,6-bis(tert-butyl)pyridine to the chiral P-spiro diaminodioxaphosphonium-mediated enantioselective protonation of ketene disilyl acetals was preferable in order to reproduce the high enantioselectivity, presumably because it could avoid the influence of the nonenantioselective background reaction by the liberated HBArF (Scheme 47).97 Fuji and co-workers described their use of nucleophilic catalyst derivative from pyridine in the kinetic resolution of a series of diol-monoesters (Scheme 48).98 In their work, only 5 mol % of catalyst was loaded with the assistance of the neutralization reagent 2,4,6-collidine, which could neutralize the generated acids but not activate the acyl reagent owing to

precatalyst and iPr2EtN as a powerful basic additive to furnish the enantioenriched polycyclic adducts. Next, the same group successfully extended this methodology to other electrondeficient Michael acceptors.84−89 In almost all examples i Pr2EtN was utilized as a necessary Brønsted base additive. In 2007, Peters and co-workers developed the nucleophilecatalyzed reaction of α,β-unsaturated acid chlorides and the trichloromethyl aldehyde to provide synthetically versatile δlactones (Scheme 42).90,91 The substituent at the β position of α,β-unsaturated acid chlorides can be varied to different aryl and alkyl groups. Moreover, the trichloromethyl group could be transformed to several useful functional groups at the δ position of the cyclization product. The added iPr2EtN could promote the formation of ketene and neutralize the in-situ-generated HX to keep the nucleophilic catalysis active. In addition, a Lewis acid additive like Sn(OTf)2 could significantly improve the yield as it could facilitate the deprotonation process and activate the aldehyde substrate. Later, Ye and co-workers demonstrated the cinchona alkaloids-catalyzed enantioselective [4 + 2] cyclization reaction of α,β-unsaturated acid chlorides with azodicarboxylate compounds (Scheme 43)92 or alkylenyloxindoles.93 In a couple of works the introduction of Et3N into the reaction could effectively promote the reaction to smoothly proceed, while it has no obvious influence on the enantioselectivities. 3.2.2. Pyridines. In recent years, along with the rapid development of organocatalysis in asymmetric reactions, Lewis bases like pyridines could be used as achiral additive for promoting the electrophile’s reactivity. A classic example in this research field is using a pyridine derivative as a key promoter to activate the acylation regent. In 2004, Jacobsen’s group reported the activation of a weak Lewis basic N-acyliminium Scheme 41. Intramolecular Michael Reaction83

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Scheme 43. [4 + 2] Cyclization92

Scheme 44. Synthesis of Tetrahydro-β-carboline94

Scheme 47. Protonation of Ketene Disilyl Acetal97

Scheme 45. Aza-Diels−Alder Reaction95

lectivities. The in-situ-generated DMAP salt could gave the best ee values of 92%, while other amines, such as pyrroline and triethylamine, did not give more promising results. The NMR study results reveled that phosphoric acid’s salts would react with catecholborane (δ = 28.73 ppm, doublet, J = 194 Hz) to generate a new boron species (δ = 6.06 ppm, singlet). The hydrogen gas evolution was also observed during the process. Next, the boron center could act as a Lewis acid center to activate the ketones, while the PO moiety acts as a Lewis base to increase the nucleophilicity of catecholborane. Then the hydride from the activated catecholborane by the PO bond would attack the activated carbonyl of ketone in a favorable chiral environment to form the enantioenriched hydroboration product and regenerate the catalyst. In 2009, Seidel and co-workers developed a strategy applying DMAP as an efficient nucleophilic catalysis in combination with a chiral hydrogen-bonding catalyst (Scheme 50).100 In the presence of DMAP, which could act as a powerful achiral Lewis base, the benzoate could be easily activated through acylpyridinium salt. The acyl-pyridinium salt is rendered chiral upon interaction of the counteranion with a chiral anion receptor such as a thiourea catalyst to form an ion pair. Furthermore, the chiral anion receptor (thiourea catalyst) is thought to impact the equilibrium between DMAP and its acylpyridinium salt. The combinational ion pair formed from the acyl group, DMAP, and the thiourea catalyst is expected to be more electrophilic and/or soluble than the sample ion pair formed by the acyl group and DMAP. The same group also employed this thiourea DMAP catalytic system in their continuous work of the kinetic resolution of amines.101−103 Later, Seidel’s group accomplished the desymmetrization of meso-diamines via enantioselective monobenzoylation facilitated by the same thiourea DMAP catalytic system, affording the monoacylated meso-diamines in good yields and good to excellent enantioselectivities (Scheme 51).104 The mesodiamines with various substitution patterns underwent monobenzoylation to yield 1,2-diamine derivatives with good

Scheme 46. Mannich Reaction96

the steric hindrance effects by the methyl group adjacent to the nitrogen atom. 3.2.3. DMAP. The Antilla group later utilized a similar combinational strategy to accomplish the asymmetric reduction of ketones using phosphoric acid DMAP salts (Scheme 49).99 The results showed that the introduction of different amines as additives would lead to dramatic changes in the enantiose4024


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Scheme 48. Kinetic Resolution of Diol-Monoester98

Scheme 49. Reduction of Ketone99

This cooperative action of DMAP and chiral thiourea catalysts was also applied to other asymmetric acylation reactions. In 2011, Jacobsen and co-workers accomplished a highly enantioselective acylation of silyl ketene acetals with acyl fluorides to afford useful α,α-disubstituted butyrolactone products (Scheme 52).105 In this work, the combination of thiourea catalyst and 4-pyrrolidinopyridine furnished a series of α,α-disubstituted butyrolactone products with high levels of enantioselectivities. They found that no reaction occurred in the absence of either thiourea catalyst or 4-pyrrolidinopyridine. This observation indicates the thiourea is playing a role in the generation of the key acylpyridinium ion intermediate. It is likely that the outstanding hydrogen-bond-accepting ability of the fluoride anion is important in this regard. Moreover, the author indicated the catalyst arene substituent might engage in a stabilizing interaction with the acylpyridinium cation intermediate in the enantioselectivity-determining acylation event. Almost at the same time, Seidel et al. reported the Steglich rearrangement of O-acylated azalactones to provide α,αdisubstituted amino acid derivatives in a highly enantioselective fashion by employing a thiourea DMAP catalytic system (Scheme 53).106 Moreover, in their work, further replacement of the nucleophilic cocatalyst for isoquinoline resulted in a divergent reaction pathway and an unprecedented transformation of O-acylated azalactones. This strategy provided highly substituted α,β-diamino acid derivatives with excellent levels of enantioselectivities. Addition of DMAP was also applied in other asymmetric reactions, such as asymmetric epoxidation. Miller and co-

levels of enantioselectivities. The author also found there are no dibenzylated products in the cooperative catalytic manner. Scheme 50. Kinetic Resolution of Amine100

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Scheme 51. Desymmetrization of meso-Diamine104

Scheme 52. Acylation of Silyl Ketene Acetal105

Scheme 53. Steglich Rearrangement106

3.2.4. Imidazoles. Miller et al. reported a MBH reaction using the combinational strategy. They found the nucleophile peptide and proline could function synergistically for the asymmetric ketone-based Baylis−Hillman reaction (Scheme 56).109 Although neither compound was effective independently in terms of rate nor enantioselectivity, their combination led to good results. Further screenings identified the peptides containing iminazole as cocatalyst would lead to good enantioselectivity. Moreover, the author found the right combination of the chiral catalyst (proline) with the cocatalyst (peptides containing iminazoles) would give higher ee values; the results indicated that a phenomenon of matched/ mismatched stereoselection is operating between these two catalysts. An interesting additive effect on the proline-catalyzed intramolecular MBH cyclization was found by Hong et al. (Scheme 57).110 In the reaction of hept-2-enedial, addition of imidazole could not only increase the reaction yield from 67% to 71% and enantioselectivity from 15% to 59% but also reverse the configuration of the product. In the presence of imidazole, it would attack the Si face of the iminium ion to form the (S)-

workers demonstrated that DMAP could accelerate the oxygen transfer event in the epoxidation reaction of olefins (Scheme 54).107 It is speculated that DMAP should act as a Lewis base and undergo fast in situ oxidation to the DMAP-N-oxide I; either DMAP or DMAP-N-oxide may function as a nucleophilic catalyst, promoting generation of peroxide intermediate, which could transform olefins to epoxides. Miller’s group also utilized the same strategy in the asymmetric oxidation of 2-aryltryptamine derivatives (Scheme 55).108 This catalytic system could tolerate broad substrate scope and functional group. 4026


Chemical Reviews

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Scheme 54. Epoxidation of Olefin107

Scheme 56. Baylis−Hillman Reaction109

Scheme 57. Intramolecular MBH Cyclization110

imidazolium, which would then undergo the cyclization and hydrolysis to afford the final product. It has been reported that imidazole could not only catalyze the syn−anti isomerization of aldol or Mannich products111,112 but also promote the double-bond isomerization. In the reaction of crotonaldehydes and imines, Tanaka and Barbas III et al. found that addition of imidazole could accelerate the isomerization of the Mannich product to form the final formal aza-MBH-type product together with the increased yield and enantioselectivity (Scheme 58).113 In the absence of an additive, the product was obtained in 35% yield, 12:1 E/Z, and 96% ee. In the presence of 1.0 equiv of imidazole, the yield increased to 65%, E/Z to 15:1, and ee to 98%. About the mechanism, it underwent the first Mannich-type reaction of insitu-generated enamines and a subsequent double-bond isomerization. Control experiments showed that imidazole could promote the Mannich product to isomerize to the azaMBH-type product and (Z)-aza-MBH product to (E)configuration.

Imidazole could be used as an acid scavenger in the NHCcatalyzed formal [4 + 2] annulation starting from carboxylic acids and Boc-aminobenzyl chloride. Scheidt et al. found that addition of 60 mol % of imidazole could significantly increase the yield from 61% to 85% with a slight improvement of enantioselectivity. It was proposed that imidazole could absorb HCl generated in situ from the formation of aza-o-quinone, thus protecting the starting materials and catalyst in the reaction (Scheme 59).114 3.2.5. DABCO and DBU. Jøgensen and co-workers demonstrated a tandem nitro-Michael/Henry reaction of a 1,3-dinucleophile. It was found that addition of a base like DABCO was necessary as the reaction rate was considerably low in the absence of DABCO (Scheme 60).115 The use of 10 mol % of DABCO was found to be more efficient with respect to yield and enantioselectivity. Introduction of a base could efficiently activate the 1,3-dinucleophile and lead to the

Scheme 55. Oxidation of 2-Aryltryptamine108

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Scheme 58. Formal Synthesis of Aza-MBH Product113

Scheme 59. Formal [4 + 2] Annulation114

Scheme 60. Tandem Nitro-Michael/Henry Reaction115

(99%. Lithium benzoate derivatives were also suitable for this reaction and gave comparable results to that with LiOAc. The positive effect of these lithium salts may be attributed to the fact that they could enhance the nucleophilicity of deprotonated nitromethane and accelerate the formation of the iminium ion. A similar additive effect on the conversion in the asymmetric Michael addition of malonate to α,β-unsaturated aldehyde was found by Pericàs140 and Ye.141 Addition of LiOAc resulted in the significant increase of conversion from 24% to >99% with reduced reaction time. Interesting, benzoic acid, a common additive for iminium-catalyzed reactions, even showed negative effects on conversion (Table 11). It was suggested that LiOAc could be used as a Brønsted base to activate the malonate.

Scheme 67. Michael Reaction132

Table 7. Annulation of Isatin with Enal133,134

entry

additive

loading (mol %)

conversion (%)

dr

ee (%)

1 2 3 4 5 6 7 8 9 10 11

Mg(OtBu)2 Ti(OiPr)4 LiCl LiCl LiCl LiCl, 12-crown-4 NaCl KCl LiBF4 LiOTf

50 50 50 50 100 200 200 200 200 200 200

99 99 99 99 99 99 99 99 99 99 99

1.1:1 1.5:1 1:1 1.8:1 2:1 2.5:1 1.2:1 1.2:1 1:1 1:1 3.7:1

34 35 52 70 77 90 35 53 47 62 39 4031


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Scheme 68. Annulation of 3-Bromoenal and Dimerization Enal135,136

Table 8. α-Aminomethylation of Aldehyde137

entry

additive

1 2 3 4 5 6 7

NaCl LiCl LiBr LiI LiClO4 LiOAc

conversion (%) 80 >95 >95 >95 >95 96 >95

Table 10. Michael Addition139

ee (%)

entry

78 72 90 96 88 74 75

1 2 3 4 5 6 7

3.3.2. Sodium Salts. Na2CO3 can be used as an additive in the phosphine oxides-involved reactions. In the presence of Na2CO3, the equilibrium between phosphine oxide and phosphinite would shift toward the reactive phosphinite. It can activate phosphine oxides to accelerate the reaction, but it cannot catalyze the reaction to take place. Nakamura et al.

additive

conversion (%)

ee (%)

LiOAc PhCO2Li 4-FPhCO2Li 4-MeOPhCO2Li 4-NO2PhCO2Li 2-NO2PhCO2Li

25 >99 >99 >99 >99 >99 >99

94 95 93 95 94 93 93

reported an obvious additive effect in the phospha-Brook rearrangement reaction. They found that when the reaction was performed without Na2CO3, the product was isolated only in 17% yield, but the yield was greatly improved to 93% with addition of Na2CO3 (Scheme 69).142,143

Table 9. Addition of Aryl Trifluoroborate to Enone138

entry

additive

yield (%)

1 2 3 4

LiCl LiBr LiI

15 53 86 10 4032

ee (%)

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Chemical Reviews

Review

Table 11. Michael Addition140,141

entry 1 2 3

additive

t (h)

conversion (%)

ee (%)

LiOAc PhCO2H

96 36 24

24 >99 8

94 90 n.d.

Scheme 69. Phospha-Brook Rearrangement142,143

Takemoto and co-workers found that NaHCO3 could affect the yield of Petasis-type reaction of quinolones (Table 12).146 In order to improve the enantioselectivity, they tried several additives. Addition of H2O gave increased enantioselectivity but with a considerable loss of the yield. Further addition of NaHCO3 improved the chemical yield. It was assumed that H2O could be used as a proton source to regenerate the catalyst and NaHCO3 as an acid scavenger to remove the resulting boronic acid. Sodium sulfate, a common drying agent, can improve the yield or enantioselectivity, as it can scavenge adventitious moisture or water generated from the reaction. In the asymmetric nucleophilic substitution reaction of 3-hydroxyoxindole with enecarbamate, Gong et al. found that addition of anhydrous Na2SO4 to the reaction improved the yield from 75% to 92%. The improved yield may be attributed to inhibition of the decomposition of the enecarbamate, which can be decomposed easily in the presence of water generated from dehydration of 3-hydroxyoxindoles (Scheme 71).147 Feng and co-workers observed the improvement of enantioselectivity in the asymmetric one-pot, three-component Strecker reaction starting from benzaldehyde, (1,1-diphenyl)methylamine, and TMSCN. In their initial studies, the best ee was 75%, probably due to the water generated from the formation of imine. In order to improve the selectivity, they screened some water scavengers, such as MgSO4, Na2SO4, and MS, and Na2SO4 gave the best result of 81% ee (Scheme 72).148 In the asymmetric oxidative sp3 C−H olefination reaction of tertiary amine with olefin, Wang et al. reported that Na2SO4 additive was capable of improving the enantioselectivity (Table 13).149 During the course of optimizing the reaction conditions, they found that addition of 4 Å MS could improve both the yield and the ee (70% yield and 81% ee), but the enantioselectivity was still not satisfactory. Further optimization revealed that addition of Na 2 SO 4 could improve the

This phenomenon was also observed in the asymmetric substitution of Morita−Baylis−Hillman carbonates with dialkyl phosphine oxides (Scheme 70). For the reactive diaryl Scheme 70. Substitution of MBH Carbonate with Phosphine Oxide144,145

phosphine oxides, the reaction proceeded efficiently without adding any Na2CO3,144 but the situation was changed when the less reactive dialkyl phosphine oxides were employed. The reaction did not occur without Na2CO3, but addition of Na2CO3 resulted in satisfactory yields and excellent enantioselectivities.145 Table 12. Petasis-Type Reaction146

entry 1 2 3

additive

yield (%)

ee (%)

H2O H2O + NaHCO3

70 27 65

90 93 94

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Scheme 71. Substitution of 3-Hydroxyoxindole with Enecarbamate147

Scheme 72. Strecker Reaction148

Wang and co-workers observed that addition of NaOAc could improve the yield of the asymmetric oxa-Michael− Michael cascade reaction.151,152 The reaction proceeded with encouraging results (65% yield, 4:1 dr, and 96% ee). Further optimization revealed that both PhCO2H and NaOAc could improve the reaction yields (78% and 80%) without changing enantioselectivity, but slightly better dr (5:1) was obtained when using NaOAc (Table 14). The same group reported that NaOAc had positive effects in the asymmetric Michael−aldol cascade reaction of cinnamaldehyde with dimethyl 2-oxoethylmalonate (Table 15).153 The reaction could proceed smoothly without any additive to afford the product in 73% yield and 91% ee, but better yield (78%) could be obtained in shorter time when adding NaOAc to the reaction. In the case of enantioselective aziridination of α,βunsaturated aldehydes, Córdova et al. found that the aziridination reaction of enal and N-tosyloxycarbamate was highly diastereoselective but with poor conversion. However, the conversion could be greatly improved to 100% when adding NaOAc to reaction, as it could be used as a base to scavenge the resulting TsOH (Table 16).154 A similar accelerated effect was observed in the aziridination of α-substituted unsaturated aldehydes.155,156 Hayashi and co-workers observed a significant additive effect in the oxidative cross-coupling of aldehydes and nitromethane.157,158 The reaction scarcely proceeded in the absence of additive or even in benzoic acid, a common additive in the diphenylprolinol silyl ether-catalyzed reactions. However, this reaction could proceed efficiently in weak basic conditions by adding some salts, such as NaHCO3, LiOAc, NH4OAc, and NaOAc. Among them, NaOAc gave the best results, affording the product in 76% yield and 92% ee (Table 17). You and co-workers found that NaBF4 played an important role in the reactivity and selectivity in the N-heterocyclic

Table 13. C−H Olefination149

entry

additive

yield (%)

ee (%)

1 2 3

4 Å MS Na2SO4 4 Å MS + Na2SO4

70 56 72

81 88 90

enantioselectivity to 88% ee but with diminished yield. While adding 4 Å MS and Na2SO4 together, a synergy effect was observed for improving both yield and enantioselectivity (72% yield and 90% ee). In the organocatalytic asymmetric fluorination/semipinacol rearrangement cascade of strained allylic alcohols, the reaction was sluggish in the absence of any additive (19% yield, 22% ee). However, on addition of Na2CO3, both yield and ee were improved (84% yield, 80% ee). Further changing the additive from Na2CO3 to Na3PO4 and lowering of the reaction temperature resulted in an increase of yield to 87% and the enantioselectivity to 90% (Scheme 73).150 Scheme 73. Fluorination/Semipinacol Rearrangement150

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Table 14. Oxa-Michael−Michael Cascade151,152

entry 1 2 3

additive

yield (%)

dr

ee (%)

PhCO2H NaOAc

65 78 80

4:1 4:1 5:1

96 96 96

Table 15. Michael−Aldol Cascade153

entry 1 2 3

Table 18. Carbene-Catalyzed Michael Addition159

additive

t (h)

yield (%)

ee (%)

PhCO2H NaOAc

18 36 12

73 54 78

91 88 90 entry

Table 16. Aziridination of Enal154

entry

additive

t (h)

conversion (%)

dr

ee (%)

1 2

NaOAc

3 0.5

73 100

20:1 15:1

n.d. 97

1 2 3 4 5 6 7

additive NaBF4 LiBF4 KBF4 NaBF4 NaBF4 NaBF4

loading (mol %)

yield (%)

ee (%)

5 5 5 10 20 50

61 80 64 63 72 62 37

16 94 85 15 90 90 89

asymmetric reactions, can also modify the reactivity of the asymmetric organocatalytic Michael reaction of cyclic dimedone and α,β-unsaturated ketone. Feng et al. observed that addition of NaBArF could improve the reaction yield from 52% to 70%, though with little loss of the enantioselectivity (Scheme 74).160

Table 17. Oxidative Cross-Coupling of Aldehyde and Nitromethane157,158

Scheme 74. Michael Reaction160 entry 1 2 3 4 5 6 7

additive

t (h)

yield (%)

ee (%)

PhCO2H NaHCO3 Na2HPO4 NH4OAc LiOAc NaOAc

48 48 48 48 48 24 24

20:1 >20:1 >20:1 >20:1 18:1 13:1 17:1

90 90 94 89 90 94 92 93 90

a

1 2a 3b 4b 5b 6b 7b 8b 9b a

R = Et. bR = Me.

of Ti(iOPr)4 was added the reaction. Further increasing the loading of Ti(iOPr)4 to 4.0 equiv and addition of 6.0 equiv of i PrOH led to an increased yield to 84%, diastereoselectivity to 20:1, and enantioselectivity to 95% (Table 26).186 The positive effect of Ti(iOPr)4 could be also observed in the asymmetric monofluoromethylation of aldehydes by Shibata (Scheme 83).187 In their initial investigation, using only thiourea catalysis afforded the product in low yield (49%) and ee (22%). They tried some additives, such as HFIP, CF3CH2OH, Er(OTf)3, PhCO2H, and 2,6-lutidine, but they all gave poor results. Fortunately, addition of 2.3 equiv of Ti(iOPr)4 could significantly improve the yield to 84% and ee to 91% in a shorter reaction time. 3.3.6. Other Salts. 3.3.6.1. ZnI2. In the guanidiniumcatalyzed asymmetric alkylation of 3-substituted oxindoles, Jiang and co-workers found that addition of ZnI2 as an additive could improve both the yield and the ee (Table 27).188 Initial studies using only guanidinium catalysis resulted in the product in 71% yield and 86% ee. In order to improve the results, they screened four additives. KI could slightly improve the yield, while ZnI2 could increase the yield to 95% and ee to 93%. In the case of FeI2 and AgI, both of them enhanced the enantioselectivity but the yield decreased apparently. 3.3.6.2. Indium Salts. An interesting switch of regioselectivity between 1,2- and 1,4-addition induced by simple swap of counteranions of indium(III) for the reaction of indoles and unsaturated keto esters has been reported by Luo.189 With phosphoric acid itself, the 1,2-adduct was favored over the 1,4addition product with moderate yield (75%), high regioselectivity (30:1), and high enantioselectivity (90% ee). Addition of 10 mol % of InF3 promoted the 1,2-addition with improved yield and ee. Interestingly, by simply changing InF3 to InBr3,

the regioselectivity was switched from 1,2- to 1,4-addition with high yield (93%), high regioselectivity (31:1), and moderate enantioselectivity (69% ee). This phenomenon seems to be independent of phosphoric acid, as a similar counteranion effect could be observed in other phosphoric acids (Scheme 84). Though the detailed mechanism was not clear, they proposed that the indium(III) metal center might be fine tuned by the halide ligands to provide specific electronic and steric properties. 3.3.6.3. Ammonium Salts. Feng190 and Moorthy191 et al. found that addition of organic salt to the amine-catalyzed Biginelli reaction had positive effects on both the yield and the enantioselectivity. Feng found tBuNH2.TFA gave the best result, while Moorthy used Ph3CNH2.TFA as the best additive (Scheme 85). Salts can modify the viscosity, permittivity, and polarity of solvents. Mioskowski et al. described a spectacular salt effect in the kinetic resolution of 1-phenylethylamine (Table 28).192 When the reaction was performed in the standard acetylation conditions, the (R)-acetamide was obtained in 60 min with 42% ee. Further adding salts to the reaction led to an increase of the reaction rate by 3−6 times and a complete reversal of stereoselectivity. Among all the studied salts, nOct3NMeCl was the most effective, giving the (S)-acetamide in 10 min with 90% ee. 3.4. Alcohols and Phenols

3.4.1. Alcohols. Simple alcohols like MeOH have been successfully used as additives in the asymmetric organocatalyzed reactions. In the cyanoethoxycarbonylation of isatins, Sakakura and Ishihara et al. found that addition of MeOH could significantly reduce the reaction time while at the same time improve the reaction yield (Scheme 86).193 Without additive, 4040


Chemical Reviews

Review

Table 25. Annulation of Cinnamaldehyde and Chalcone181,182

entry 1 2 3 4a a

additive 1 Ti(iOPr)4 Ti(iOPr)4 Ti(iOPr)4

additive 2

i

PrOH PrOH

i

yield

cis:trans

ee (%)

73 47 75 74

1:3 20:1 20:1 20:1

99

Using a chiral N-heterocyclic carbine.

Scheme 82. Dimerization of Enal183

enon, that different grade solvents delivered significant differences to both the yield and the enantioselectivity (Table 29).194 Analytical reagent-grade solvent gave the product in 92% yield and 68% ee, while HPLC grade led to the reduced yield of 8% and ee of 46%. The key to this difference might lie in that AR-grade CHCl3 containing trace EtOH (0.6−1.0% v/ v). In order to confirm this suspicion, they conducted control

the reaction proceeded in 48 h to afford the product in 87% yield, while addition of MeOH reduced the time to 2 h with improved yield to 98%. Addition of MeOH was proposed to dissociate the oligomer of the catalyst to give the active monomer, thus leading to the increased reactivity. In the case of asymmetric bromolactamization of olefinic amides, Yeung and co-workers found an interesting phenom4041


Chemical Reviews

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Table 26. Annulation of Enal and Unsaturated Ketoester186

entry

additive 1

1 2 3 4

Ti(iOPr)4 (2 equiv) Ti(iOPr)4 (2 equiv) Ti(iOPr)4 (2 equiv)

additive 2

yield

cis:trans

ee (%)

PrOH (6 equiv) i PrOH (6 equiv)

0 68 63 84

7:1 18:1 20:1

90 96 95

i

Scheme 83. Monofluoromethylation of Aldehyde187

Table 27. Alkylation of 3-Substituted Oxindole188

entry 1 2 3 4 5

additive

yield (%)

ee (%)

KI ZnI2 FeI2 AgI

71 81 95 26 43

86 87 93 92 91

preferred product in 97% yield and 90% ee, with a trace of propargylamide and hemiaminal (95 >95

31 80 88 81

with acetaldehyde or acetone as observed by Nakamura296 and Toru297 et al. The reaction with water gave the product with a higher enantioselectivity of 96% than that of 78% without water (Scheme 122). In the case of proline amide-catalyzed aldol reaction of aldehydes with hydroxyacetone, Gong and co-workers found that addition of water could change the regioselectivity of the reaction (Table 40).298 When the reaction was conducted in THF without water, mixtures of two isomers of 1,4- and 1,2diol were obtained in 36% and 58% yield, respectively. In contract, when using wet THF, the isomer 1,4-diol was obtained dominantly in 92% yield. About the mechanism, theoretical studies revealed that the hydrogen bonds between

water and the amide oxygen and hydroxyacetone played an important role in controlling the regioselectivity. The above hydrogen bonds made the enamine more much favorable than enol−enamine in the presence of water. The role of water on the yield and enantioselectivity was investigated by Wang in the amine-catalyzed Michael reaction of ketones to nitroolefins (Scheme 123).299 The reaction without water gave the product with 87% yield and 65% ee, but addition of 15 mol % of water improved the yield to 92% and ee to 72%. They proposed that addition of water could increase the turnover of the catalyst by releasing the catalyst from the imine intermediate.

Scheme 115. Reaction of Allenoate and Imine270,271

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Chemical Reviews

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Scheme 117. Steglich and Black Rearrangement275

Miller et al. observed a significant additive effect of water in the protected cysteine-catalyzed Rauhut−Currier reaction (Table 43).304 The amount of water was a critical factor for the enantioselectivity. In the absence of water, the product was obtained with an ee of 32%, while addition of 1.0 equiv of water improved the ee to 42%. Further increasing the amount of water to 20 equiv led to a dramatic increase of ee to 81%. However, when the amount was in excess of 20 equiv, addition of water had a deleterious effect. For example, the ee dropped dramatically to 33% when 100 equiv of water was added. In the chiral primary amine thiourea promoted conjugate addition of α,α-disubstitued aldehydes to nitroalkenes; Jacobsen and co-workers found that addition of controlled amounts of water was beneficial for optimal yield, probably by affecting the imine and enamine formation and imine hydrolysis steps (Table 44).305 The reaction proceeded in 34% yield in the absence of water. The yield could be improved to 56% or 64%, respectively, by adding 2.0 or 5.0 equiv of water, but further increasing the amount of water led to a decreased yield of 54%. The same group also observed similar effects of water in amine thiourea-catalyzed addition of ketones to nitroalkenes306 and αalkylation of α,α-disubstitued aldehydes.307 The use of water as an additive was essential for high yield and enantioselectivity in the asymmetric hydrosilylation of βenamino esters,308 β-amino nitroolefins,309 and indoles310 with trichlorosilane. Take the reduction of β-enamino esters for example; the reaction proceeds with a good enantioselectivity of 91% but rather low yield of 30%, due to the fact that the trichlorosilane could only reduce imines not their enamino tautomerizations. Therefore, the yield might be improved by the promotion enamine−imine isomerization. To test this hypothesis, the authors tried some protic additives as they could promote the isomerization by the protonation. Delightfully, most of them could accelerate the reaction to give a better yield. In particular, addition of 1.0 equiv of H2O gave the best results of 98% yield and 96% ee. Further reducing or increasing the amount of water caused a decrease in yield (Table 45). In this reaction, H2O was used to react with moisture-sensitive trichlorosilane to generate a strong Brønsted acid HCl, which could promote the formation of imine isomer.

Jørgensen and co-workers found that addition of water was essential for amine-promoted α-arylation of aldehydes (Table 41).300 The reaction did not work in dry DMSO, but using wet DMSO dramatically accelerated the reaction to complete with full conversion with an ee of >99%. Furthermore, this reaction could be conducted in H2O or EtOH with full conversion with a slight loss of enantioselectivity. In the case of amine-catalyzed aza-Diels−Alder reaction of aldehydes, Chen et al. found that addition of water could significantly accelerate the reaction (Table 42).301 In their initial optimization of the reaction, the desired product P1 was obtained in poor yield (10:1

89 97 97 98 99 >99 >99 >99 96

Scheme 122. Aldol Reaction of Isatin296,297

Scheme 120. α-Amination of 3-Substituted Oxindole288

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Chemical Reviews

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Table 40. Aldol Reaction298

entry

solvent

yield of P1 (%)

ee of P1 (%)

yield of P2 (%)

1 2

THF THF/H2O

36 92

97 90

58 7

Scheme 123. Michael Reaction299

example, in the case of imidazolinone-catalyzed asymmetric Michael reaction of N-methylindole with an α,β-unsaturated aldehyde, the reaction proceeded in 19% yield and 81% ee, while the use of N-phenyl-N′-[3,5-bis(trifluoromethyl)]phenyl thiourea greatly increased the yield to 81% with almost the same enantioselectivity of 79% (Scheme 128). The thiourea additives could also be used as cocatalysts to activate the substrate. In the formal [2 + 2] cycloaddition of enals with nitroalkenes, the combination of chiral amine catalyst with PhCO2H afforded the product in a promising yield of 59% and enantioselectivity of 74%. In order to improve the results, Vicario et al. tried the dual-activation strategy by addition of achiral thiourea. Gratifyingly, the combination of chiral amine catalyst with achiral thiourea could lead to an increased yield of 86% and ee of 91%. In this study, the thiourea was proposed to activate the nitroalkene by double hydrogen bonding in the initial Michael reaction (Scheme 129).319 Addition of an achiral thiourea additive was necessary for high enantioselectivity in the intramolecular [5 + 2] cycloaddition (Scheme 130).320,321 In the absence of an additive, the reaction proceeded in 37% yield and 21% ee. A significant additive effect was observed when adding the achiral thiourea (53% yield and 67% ee). On the basis of some control experiments, they proposed that the reaction started with the condensation of aminothiourea with the ketone of the substrate to form the dienamine intermediate, and subsequent

Table 41. α-Arylation of Aldehyde300

a

entry

solvent

conversion (%)

ee (%)

1 2 3 4

DMSO (dry) DMSO (7% H2O) H2O EtOH (7% H2O)

n.r. 100 (86)a 100 (99)a 100 (75)a

>99 93 95

Isolated yield.

which could then disperse the negative charge and separate the ion pair of the iminium cation. Therefore, this strategy could improve the catalytic activity of iminium catalysis.317,318 For Table 42. Aza-Diels−Alder Reaction301

entry

solvent

1 2 3 4 5

toluene THF MeOH CH3CN CH3CN

H2O (%)

t (h)

yield (%)

ee (%)

10

72 72 72 72 24

10:1 >10:1

96 96 96 96

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Chemical Reviews

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Scheme 126. Aldol or Michael Reaction312,313

Scheme 127. Aldol Reaction315,316

Scheme 128. Michael Reaction317,318

Scheme 129. Formal [2 + 2] Cycloaddition319

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Chemical Reviews

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Scheme 130. [5 + 2] Cycloaddition320,321

Scheme 131. Acetalization/Oxa-Michael Cascade322

3.8.2. BBr3. Generally speaking, the acidity of chiral phosphoric acids is not strong enough to activate the aldehydes, due to their lower basicity. Ishihara et al. solved this problem by adding an achiral Lewis acid to the chiral phosphoric acid in the enantioselective Diels−Alder (DA) reaction of α-substituted acroleins with 1,2-dihydropyridines (Table 46).327 As expected, the reaction was slow and led to poor enantioselectivity without the Lewis acid additive. Gratifyingly, addition of BX3 could greatly improve both the yield and the selectivity. Among them, BBr3 gave the best results of 99% yield, endo:exo ratio 2:98, and 89% ee. Furthermore, the amount of BBr3 was also vital, as the yield or/and enantioselectivity decreased significantly when the amount was more or less than that of phosphoric acid. 3.8.3. (Boc)2O. The in-situ Boc-protection strategy by using (Boc)2O additive was recently reported by Seidel et al. in the asymmetric Pictet−Spengler reaction with unmodified tryptamines (Scheme 134).328 In the initial study without any additives, the best was obtained with an excellent enantioselectivity of 94% but the yield was low (37%). Due to product inhibition, the yield could not be improved by simple extension of the reaction time. Trying to improve catalyst turnover, they used two strategies by adding achiral acid and (Boc)2O additives to reduce the product inhibition. The acid additive strategy was based on the concept that an acid which was unable to promote to racemic background reaction could protonate the product to form the product salts, thus facilitating catalyst turnover. Among the tested acids, malonic acid provided the best result of nearly quantitative yield (>95%) and 93% ee. The second strategy was the in-situ Boc protection of the product, which could also reduce the degree of product inhibition. This strategy was also viable and efficient as excellent results of 95% yield and 92% ee were obtained in reduced catalyst loading of 10 mol %. It should be noted that N-Boctryptamine does not undergo formation of products. Addition of (Boc)2O was also efficient in the disulfonimidecatalyzed reduction of N-alkyl imines (Scheme 135).329 Although an excellent enantioselectivity of 91% was obtained in the absence of an additive, the yield was low, due to the catalyst deactivation by the formation of salt with the product amine. In order to avoid this product inhibition, the authors investigated the additive effect of (Boc)2O. Remarkably, the yield was greatly improved to 97% without any loss of enantioselectivity. Other protection reagents like acetic

Scheme 132. Fischer Indolization323−325

In this reaction, Amberlite CG50 was used to trap ammonia by cation exchange, thus renewing the turnover of the catalytic system. Addition of CG50 was also beneficial for phosphoriccatalyzed dearomatizing redox cross-coupling of ketones with aryl hydrazines (Scheme 133).326 4060


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Scheme 133. Dearomatizing Redox Cross-Coupling326

Table 46. Diels−Alder Reaction327

entry

additive

x (mol %)

yield (%)

endo:exo

ee (%) (exo)

1 2 3 4 5 6 7 8

B(C6F5)3 BF3 BCl3 BBr3 BBr3 BBr3 BI3

5 5 5 2.5 5 10 5

51 64 87 88 92 99 64 98

13:87 10:90 3:97 4:96 3:97 2:98 8:92 7:93

−7 5 52 62 61 89 18 37

adding an additive. In sharp contrast, the desired product was obtained quantitatively (99% yield) with moderate enantioselectivity when adding trichloroacetonitrile to the above reaction system. Addition of Cl3CCN was proposed to form the peroxyhemiaminal intermediate, of which the amidate ion could be left easily, thus leading to swift conversion of final product. 3.8.6. 18-Crown-6. In the enantioselective alkylation of tert-butyl glycinate Schiff base with benzyl bromide under the catalysis of chiral ammonium salt, a dramatic rate enhancement occurred by adding 18-crown-6 (Scheme 138).334 The reaction was sluggish and gave the product in only 8% yield and 94% ee, while adding 18-crown-6 dramatically increased the yield to 98% with a slight improvement of ee to 98%. Similar-sized analogues of 18-crown-6 showed similar reactivity and enantioselectivity, but smaller-sized crown ethers such as 15crown-5 and 12-crown-4 dramatically lowered the yield. In addition, tetrabutyl- and tetraoctylammonium bromide also gave a relatively high yield and enantioselectivity. In this reaction, the rate enhancement would be attributed to the ability of 18-crown-6 to extract potassium cation into the organic phase, thus accelerating the slow deprotonation process of glycinate Schiff base.

anhydride (Ac2O) and dibenzyl dicarbonate (Cbz2O) could also be used in this reaction. 3.8.4. Bromine Salt. In the asymmetric bromocyclization of tryptophol using accessible bromine salts derived from DABCO, Xie and co-workers found both the yield and the enantioselectivity could be improved with reduced reaction time by adding a catalytic amount of DABCO-derived brominating reagent (Scheme 136).330,331 Without an additive, the reaction proceeded in 17 h to give the product in 94% yield and 81% ee. After addition of a bromine salt, the product could be obtained in 97% yield and 98% ee in a shorter reaction time of 3 h. The function of additive was clear, as no new bromine species was generated by mixing additive and reactive bromine salts. They deduced that some reactive bromium species might be produced gradually as the reaction proceeded, thus inhibiting the uncatalyzed reaction. 3.8.5. Cl3CCN. It has been reported that even Cl3CCN could be used as an efficient additive in the asymmetric oxidation of N-sulfonyl imines (Scheme 137).332,333 Ooi and co-workers observed that only a trace amount of the desired product was formed when the reaction was conducted in the presence of chiral iminophosphorane, imine, and H2O2 without 4061


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Scheme 134. Pictet−Spengler Reaction328

Scheme 135. Reduction of N-Alkyl Imine329

Scheme 136. Bromocyclization of Tryptophol330,331

Scheme 137. Oxidation of N-Sulfonyl Imine332,333

3.8.7. HOAt or HOBt. It has been reported that the use of nucleophilic additives like HOAt or HOBt facilitates the NHCcatalyzed amidation reaction of aldehydes and amines, as they

could be involved in the redox step to form the activated ester, which would undergo in-situ amidation (Scheme 139).335,336 4062


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Scheme 138. Alkylation334

reaction of aromatic aldehydes, enals, and α-aminocyanoacetate (Scheme 141).338 Without any additive, the reaction predominantly gave the Michael product in 55% yield, 1:1 dr, 92% ee, and 96% ee, together with a small amount of the cycloaddition product pyrrolidine in 15% yield, 19:1 dr, and 73% ee. In order to improve the yield of the cycloaddition product, Córdova et al. tried some hydrogen-bond-donating additives. Pleasingly, the reaction became chemospecific, as no Michael adduct was formed in the presence of hydrogen-bond-donating additive. Notably, they found oxime methyl 2-cyano-2-(hydroxyimino)acetate could significantly reduce the reaction time and improve the diastereoselectivity. Addition of oxime was reported to accelerate imine formation by pushing the equilibrium of the reaction toward imine formation. It was likely that oxime could activate the imine and its enolate intermediate and lock their conformation by intramolecular hydrogen-bonding network. 3.8.9. Silica Gel. Silica gel has been successfully used as an additive in the amine-catalyzed asymmetric inverse-electrondemand hetero-Diels−Alder reaction (Scheme 142).339 The reaction of aldehyde with enone only gave the intermediate instead of the desired product. After addition of silica gel, the intermediate adduct could be easily hydrolyzed by silica gel to give the hemiacetal product and amine catalyst. In this reaction, silica gel was used to accelerate the hydrolysis step and improve the catalytic turnover. 3.8.10. Trialkyl Phosphite. The influence of trimethyl phosphite additive on the yield and enantioselectivity of the crossed-conjugate addition between nitroalkenes and enals was reported by Shi et al. (Scheme 143).340 The cross-coupling afforded the product in a rather low yield of 12% without any additive because the epimerization process of the stereogenic center adjacent to the nitro group was easy to occur. However, addition of (MeO)3P, the product was obtained with an improved yield of 64% and ee of 90%. It was proposed that it could help activation of the nitroalkenes as a Lewis base. Further addition of AcOH improved the yield to 90% and ee to 93%, as it could promote iminium formation. The positive effect of triethyl phosphite on both yield and enantioselectivity had been observed in the asymmetric

Scheme 139. Amidation of Aldehyde335,336

Similarly, Smith et al. found that HOBt also had positive effects on the yield and selectivity in the isothiourea-catalyzed [2,3]-rearrangement of allylic ammonium ylides (Scheme 140).337 Addition of HOBt led to an increase of yield from 61% to 76%, dr from 92:8 to >95:5, and ee from 95% to 99%. To rationalize the positive effect of HOBt, it was proposed to react with acyl isothiouronium intermediate to form an active ester, thus facilitating amide bond formation. 3.8.8. Oxime. Oxime is a hydrogen-bond-donating additive, which is essential in the amine-catalyzed three-component Scheme 140. [2,3]-Rearrangement of Allylic Ammonium Ylide337

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Scheme 141. Three-Component Reaction338

Scheme 142. Hetero-Diels−Alder Reaction339

hydroxylation of 3-substituted oxindoles by Itoh and coworkers (Table 47).341 In the absence of an additive, the Table 47. Hydroxylation of 3-Substituted Oxindole341

entry 1 2 3 4

Scheme 143. Crossed-Conjugate Addition340

(EtO)3P (equiv)

t (h)

yield (%)

ee (%)

2.0 4.0 10.0

4 4 2.5 2.5

71 86 98 97

56 83 85 85

reaction proceeds in 71% yield and 56% ee, whereas addition of 2.0 equiv of (EtO)3P led to an increase of yield to 86% and ee to 83%. Increasing the amount of (EtO)3P to 4.0 equiv improved the yield to 98% and ee to 85% in reduced reaction time, but further increasing the amount of (EtO)3P to 10.0 equiv had little effect on the results. A binary catalyst system was designed by Denmark and coworkers for enantioselective bromocycloetherification of 5arylpentenols (Scheme 144).342 SPPh3 acted as a Lewis base additive for the activation of the bromine source, and the chiral Brønsted acid would replace succinimide as the counterion of the bromonium intermediate and direct the stereocontrolling 4064


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Scheme 144. Bromocycloetherification of 5-Arylpentenol342

Scheme 145. Pictet−Spengler Cyclization343−345

Scheme 146. Addition of Indole to Hydroxylactam346

Scheme 147. Addition of Thiol to Ketimine of Isatin347

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4. ADDITIVE EFFECTS ON METAL-CATALYZED ASYMMETRIC REACTIONS

cyclization process of the bromocycloetherification reaction. The author also found the site selectivity of the 5-arylpentenols is highly dependent upon the configuration of the double bond and the aromatic substituents. 3.8.11. TMSCl or TMSOH. The interaction between halide anions and thioureas have been applied in halide-producing reactions. Jacobsen et al. investigated halide binding catalysis in the enantioselective Pictet−Spengler cyclization of β-indolyl ethyl hydroxylactams (Scheme 145).343−345 They found that addition of TMSCl afforded the products in higher conversion and enantioselectivity. Experimental observations showed that the corresponding chlorolactam was formed when mixing hydroxylactams with TMSCl. It was proposed that the symmetric induction came from the initial displacement of chloride, followed by an asymmetric cyclization. In their subsequent study Jacobsen et al. expanded this reaction to the intermolecular addition of indoles to hydroxylactams (Scheme 146). Similarly, addition of TMSCl was essential for this reaction, as no reaction was observed in the absence of TMSCl. Addition of water was also beneficial for the reactivity. The synergistic effect of both TMSCl and water suggested that the in-situ-generated HCl led to formation of a chlorolactam, which was proposed to be the actual substrate in the reaction. It should be noted that addition of HCl alone gave comparable enantioselectivity but with a slower reaction rate.346 In the asymmetric addition of thiols to ketimine of isatins, Nakamura et al. found that the use of protic additives could improve both the yield and the enantioselectivity (Scheme 147).347 Without an additive, the reaction afford the product in 85% yield and 86% ee. Addition of MeOH or iPrOH could increase either the yield or the enantioselectivity. Interestingly, addition of TMSOH led to the improved results of 99% yield and 91% ee. 3.8.12. Vinyl Ethyl Ether. You et al. demonstrated that addition of vinyl ethyl ether was beneficial for the cascade isomerization/asymmetric Pictet−Spengler reaction of Nallyltryptamine by sequential catalysis of ruthenium alkylidene and chiral phosphoric acid (Scheme 148).348 In the absence of

4.1. Acids in Metal-Catalyzed Asymmetric Reactions

4.1.1. Carboxylic Acids. In 2003, Trost et al. demonstrated that acid additives could play a significant role in palladiumcatalyzed dynamic kinetic asymmetric cycloaddition of isocyanates to vinylaziridines (Table 48).350 In their study, they found that introduction of 10 mol % acetic acid to the catalytic system could increase the ee from 41% to 82%. They interpreted that the additive effect might depend on the pKa of the additive. A reasonable rationalization relates to the requirement that equilibration of the diastereomeric π-allyl palladium intermediates must be faster than cyclization to achieve high ee in a DYKAT. The same group later disclosed that addition of 1.0 equiv of acetic acid could dramatically affect the Pd-catalyzed intramolecular asymmetric allylic alkylation (AAA) of phenol allyl carbonates.351 As shown in Table 49, when no additive was used, the reaction could provide corresponding adducts in 95% yield and 14% ee, favoring formation of (S)-chroman in the presence of 2 mol % Pd2dba3 chloroform complex and 6 mol % ligand. Interestingly, the ee was dramatically enhanced (84% ee) when 1.0 equiv of acetic acid was added. It is particularly worth noting that the absolute configuration of chroman was reversed to R. It was found that benzoic acid could also give similar results in the same reaction. In rare earth metal-catalyzed asymmetric reactions, carboxylic acids were realized as very efficient additives. Ishihara et al. reported that AcOH or iPrCO2H was the key to promoting chiral lanthanum(III)-binaphthyl disulfonate complexes-catalyzed enantioselective Strecker reaction of aldimine with TMSCN (Scheme 149).352 Without any additive, the reaction gave the product in 22% yield and 65% ee, while addition of 50 mol % of iPrOH greatly increased the yield to 86% and ee to 84%. It should be noted that an amount of iPrOH less or more than 50 mol % had a corrosive role on the reactivity. They interpreted that the role of acid additive was to provide a counteranion for La(III) and generate HCN, which was actually a cyanide source rather than TMSCN, via a proton exchange reaction. In the copper-catalyzed enantioselective conjugate addition of boron to α,β-unsaturated carbonyl compounds, Kobayashi et al. found addition of acid additives could improve both the yield and the enantioselectivity (Table 50).353 The use of acetic acid, trifluoroacetic acid, or boronic acid was effective, and acetic acid gave the best result of 93% yield and 89% ee. It should be noted that though AcOH may react with Cu(OH)2, formation of Cu(OAc)2 was impossible in this reaction, as the best results were obtained with a 1:1 mixture of Cu(OH)2/AcOH. In the iridium-catalyzed asymmetric allylic substitution of allylic carbonates, Carreira et al. found that addition of acids was beneficial for both the yield and the enantioselectivity (Table 51).354 The use of citric acid as the additive led to an increase in the yield from 17% to 46% and ee from 93% to 99%. Further addition of Sc(OTf)3 as the additive could increase reaction rate, leading to a higher yield. Brønsted acid additives were found to be crucial to many rhodium-catalyzed asymmetric reactions. Krische et al. discovered that a Brønsted acid greatly benefits direct reductive coupling of conjugated alkynes and α-ketoesters and glyoxalates via rhodium-catalyzed asymmetric hydrogenation (Scheme 150). This was inspired by the phenomenon that older batches

Scheme 148. Cascade Isomerization/Pictet−Spengler Reaction348

an additive, the product was obtained in only 16% yield and 86% ee due to the fact that ruthenium alkylidene could not promote the isomerization of internal olefin effectively. On the basis of the previous study that ruthenium hydride, which could be formed in situ from the decomposition of ruthenium alkylidene and vinyl enol ethers, was responsible for the isomerization,349 they tried to add vinyl enol ethers, such as vinyl trimethylsilyl ether and vinyl ethyl ether, to the reaction. Gratifyingly, addition of 1.0 equiv of vinyl ethyl ether increased the yield to 58% with slight loss of enantioselectivity. 4066


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Table 48. Cycloaddition of Isocyanate to Vinylaziridine350

entry 1 2 3 4 5 6

additive (mol %)

conversion (%)

yield (%)

ee (%)

pivalic acid (6) AcOH (6) AcOH (10) formic acid (6) TFA (6)

100 100 100 100 100 98

98 98 99 99 98 84

41 77 80 82 77 70

Table 49. Asymmetric Allylic Alkylation351

entry 1 2 3 4 5

additive (mol %)

yield (%)

ee (%)

configuration

Et3N AcOH PhCO2H H3PO4

95 96 94 98 99

−14 −22 84 75 −5

S S R R S

Scheme 149. Strecker Reaction of Aldimine352

cleavage of the rhodium−oxygen bond not a rhodium−carbon bond.356 In addition to the vicinal dicarbonyl compounds, they also extended this catalytic system to the heterocyclic aromatic aldehydes and ketones (Scheme 151).357 To shed light on the mechanistic insight into the role of Brønsted acid additives, they performed the reductive coupling of enyne to 2-pyridine carboxaldehyde using an achiral rhodium catalyst in the presence of BINOL-derived chiral phosphoric acid. Remarkably, the coupling product exhibited substantial levels of optical enrichment (82% ee). These data are consistent with a catalytic mechanism in which the Brønsted acid cocatalyst protonates and/or forms a strong hydrogen bond to 2-pyridinecarboxaldehyde in advance of the stereogenic C−C bond-forming event. Further, the high levels of optical enrichment suggest that the LUMO lowering effects of protonation and/or hydrogen bonding dramatically accelerate the rate of C−C coupling. A similar effect was observed in the chirally modified cationic rhodium-catalyzed hydrogenation of acetylenic aldehydes (Scheme 152).358 In this process, the use of 5 mol % of 2naphthoic acid could increase the yield from 24% to 67% and the ee from 95% to 98%. The additive was proposed to assist cleavage of the rhodium−oxygen bond of metallacyclic intermediate. In an iron-catalyzed asymmetric Mukaiyama aldol reaction in aqueous conditions, benzoic acid additive was found critical to both the reaction yield and the selectivity (Scheme 153).359

of solvent DCE gave better chemical yields, in which adventitious HCl may promote reductive coupling.355 Thus, they screened an assay of Brønsted acid additives and found that 1 mol % of triphenylacetic acid could highly improve the reaction, giving 88% yield and 90% ee in freshly distilled DCE. In the absence of the Brønsted acid additive but under otherwise identical conditions, the product was produced in only 42% yield and 87% ee. Using 50 mol % of acid additive afforded the same monodeuteration product as using 1 mol %, which suggested that the reaction proceeds via protonolytic 4067


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Table 50. Addition of Boron to Unsaturated Carbonyl Compound353

entry 1 2 3 4 5 6 7

additive

yield (%)

ee (%)

AcOH TFA PhCO2H H3BO3 pyridine AcOK

84 93 93 86 94 72 90

80 89 86 81 87 70 81

Table 51. Allylic Substitution of Allylic Carbonate354

entry 1 2 3 4 5

additive (mol %)

yield (%)

ee (%)

HCO2H (200) citric acid (100) citric acid (100) + Sc(OTf)3 (1) citric acid (30) + Sc(OTf)3 (0.5)

17 46 48 50 47

93 99 99 99 99

Scheme 150. Reductive Coupling of α-Ketoesters355,356

When no additive was used, only 44% yield, 76:24 diastereoselectivity, and 8% ee were obtained. Remarkably improved results (98% yield, 97:3 dr, and 97% ee) could be obtained after adding 6 mol % of benzoic acid additive to the reaction system. Ma et al. represented a copper-catalyzed enantioselective αalkynylation of tetrahydroisoquinolines with aldehydes and terminal alkynes in which addition of 5 mol % of benzoic acid

could improve the reaction yield from 84% to 98% (Scheme 154).360 The benzoic acid derivative can also benefit Ni-catalyzed asymmetric reductive acyl cross-coupling reaction of acid chlorides and racemic secondary benzyl chlorides (Scheme 155).361 Without an acid additive, the reaction afforded the cross-coupling product (CP) in 52% yield and 94% ee, together with the rac- and meso-homocoupling product (HP) in 22% 4068


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Scheme 151. Reductive Coupling of Heterocyclic Aromatic Aldehyde357

Scheme 152. Hydrogenation of Acetylenic Aldehyde358

which could increase the ee from 85% to 95% under otherwise identical conditions (Scheme 156).362 Krische et al. disclosed that m-nitrobenzoic acid functioned as an efficient additive in reductive coupling of allyl acetate to allylic alcohols (Scheme 157).363 Whereas only 8% yield and 47% ee were obtained without use of any additive, 71% yield and 91% ee could be furnished by adding 10 mol % of mnitrobenzoic acid additive. It was particularly worth noting that configuration inversion was observed after addition of an additive. This phenomenon suggested that m-nitrobenzoic acid and the iridium center were intimately associated during the enantiodetermining carbonyl addition event. On the basis of these data it was postulated that iridium and m-nitrobenzoic acid react to form an ortho-cyclometalated complex, which serves as the active catalyst. Bolm et al. reported an iron-catalyzed asymmetric sulfide oxidation (Scheme 158).364,365 Without any additives, the sulfoxide product was obtained in 41% yield and 59% ee. Gratifyingly, addition of an acid additive like benzoic acid could increase the efficiency of the reaction. After examining 18 acid additives with different electronic and steric properties, they found 4-methoxybenzoic acid was best and afforded the product in 66% yield and 80% ee. On the basis of the phenomenon that the best enantioselectivity was obtained with an acid/[Fe(acac)3] ratio of 0.5:1 and a positive nonlinear effect, they proposed a monocarboxylate-bridged diiron(III) intermediate, which was similar to methane monooxygenase for the catalytic cycle of the oxidative process. 4.1.2. Chiral Acids. It has been reported that the acids could play a key positive role in iron-catalyzed asymmetric

Scheme 153. Mukaiyama Aldol Reaction359

yield. Addition of 2,6-dimethylbenzoic acid (DMBA) could greatly improve the yield of CP to 85% and depress the side reaction of homocoupling to the yield of 4%. In the case of N,N′-dioxide−Sc(III) complex-catalyzed asymmetric Friedel−Crafts alkylation of indoles to ethyl glyoxylate, Feng et al. discovered that o-chlorobenzoic acid had a beneficial effect on the enantioselectivity of the reaction, 4069


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Scheme 154. α-Alkynylation of Tetrahydroisoquinoline360

Scheme 155. Reductive Acyl Cross-Coupling361

Scheme 156. Friedel−Crafts Alkylation of Indole362

electronic and spatial properties (Scheme 159).369 While only 20% yield and 46% ee were obtained without use of any additive in the catalytic system, 97% yield and 86% ee could be provided when 3 mol % of chiral carboxylic acid (S)-ibuprofen was added. They also found that both the carboxylate moiety and the proton were essential for high activity as the use of sodium acetate instead of acetic acid led to the greatly reduced yield from 87% to 6%. About the mechanistic interpretation of acid,370−372 Bryliakov and Talsi et al. explained that the hydroperoxo complex I could exchange its ligand S with the acid to form the reactive complex II, whose O−O bond could be heterolyzed by the assistance of acid, as the concentration of III was increased while increasing the amount of added acid.370 Chiral acid was also found to be particularly effective in the chiral Ti-complex-catalyzed enantioselective hetero-Diels− Alder reaction of Danishefsky’s diene and aldehydes (Scheme 160).373 Inspired by a serendipity that aged aldehyde showed better reactivity and selectivity, Ding et al. screened 36 carboxylic acids as additive and found that chiral carboxylic acid, (S)-(+)-2-(6-methoxy-2-naphthyl)propionic acid (Naproxen), was the most effective additive, giving 2-substituted 2,3dihydro-4H-pyran-4-one in up to 97% ee and 99% yield. Additionally, the use of Naproxen could accelerate the reaction by one order of magnitude. The carboxylic acid additive was proposed to participate in the coordination of titanium catalyst.

Scheme 157. Reductive Coupling363

Scheme 158. Sulfide Oxidation364,365

epoxidation.366−368 Costas et al. studied the acid effects by using different carboxylic acid additives differing in the 4070


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Scheme 159. Epoxidation369,370

Scheme 160. Hetero-Diels−Alder Reaction373

Scheme 161. Mannich-Type Reaction374

4.1.3. Sulfonic Acids. The use of a catalytic amount of TfOH as an additive was important for improving the yield and stereoselectivity of La(OTf)3/MePyBox/TMEDA-catalyzed asymmetric Mannich-type reaction of imines and γ-butenolides (Scheme 161).374 In their initial study Matsunaga and Shibasaki et al. found the reproducibility was low due to a small amount of TfOH in La(OTf)3. Using carefully flame-dried La(OTf)3

without adding any acid, the reaction gave the product in 56% yield, 93:7 dr, and 66% ee. After addition of 10 mol % of TfOH, better results of 86% yield, 96:4 dr, and 79% ee were obtained. To shed light on the role of TfOH, 1H NMR spectra of the La(OTf)3/Me-PyBox/TMEDA mixture at a ratio of 1:1:2 in CDCl3 with and without TfOH were obtained. The results showed that TfOH would support the generation of the 4071


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Scheme 162. Multicomponent Reaction375

propanation of alkenes with α-cyano diazoacetamide (Scheme 163).377 Whereas a series of Brønsted acids, such as carboxylic acids, phosphoric acid, phenol, aniline, or benzamide et al., did not give positive results for the enantioselectivity of the reaction, sulfonamides were fortunately found as effective additives for the transformation. In particular, good yield and excellent selectivities (96:4 dr and 95% ee) were furnished by adding 10 mol % of TfNH2 as superior additive. Although the detailed role of TfNH2 in increasing the ee and dr was unclear, the authors claimed that TfNH2 did not undergo ligand exchange or complexation with Rh2(S-NTTL)4 but interacted with the cyano moiety of the substrate. This proposition was supported by the control experiments. 4.1.4. Phosphoric Acids. Gong et al. found addition of acid additive was successful for asymmetric allylic alkylation of pyrazol-5-ones with allylic alcohols (Scheme 164).378 The reaction cannot proceed in the absence of a Brønsted acid additive. However, the combination of (R)-phosphoric acid and (R)-phosphoramidite ligand could afford the product in 85% yield and 90% ee, whereas (S)-phosphoric acid and (R)phosphoramidite ligand led to reduced yield and ee, suggesting there existed a “match/mismatch” effect. Addition of achiral Brønsted acids like TFA or p-TSA gave significantly diminished yields. About the mechanism, it was suggested that the acid could (1) activate cinnamic alcohol by expelling the hydroxy group to cationic π-allylpalladium complex and (2) serve as a Lewis base to activate pyrazol-5-one by enolization. It has also been reported that the achiral phosphoric acid can have a positive effect in the palladium-catalyzed-directed intermolecular fluoroarylation of styrenes (Scheme 165).379 In the initial reaction using simple achiral ligand, Toste et al. found addition of an organic phosphate could improve the reaction yield and diminish the impurities. When using a chiral ligand, the reaction afforded a range of benzylic fluorides in good yield and high enantiomeric excess. 4.1.5. Inorganic Acids. Zhang et al. presented a chiral Rhcomplex-catalyzed asymmetric hydrogenation of ethyl 2-oxo-4arylbut-3-enoates380 and 2-oxo-4-phenylbutanoic acids381 in which Brønsted acids, particularly 1 M aq HBr, could be a s highly efficient additive in the transformation. Control experiments revealed that the combination of Brønsted acid and water in the catalytic system is superior to either of them in terms of reaction rate and enantioselectivity (Scheme 166).

desirable active species La(OTf)3/Me-PyBox/TMEDA (1:1:1) and thereby promote the reaction. In a cooperative catalytic multicomponent reaction (MCR) between methyl phenyldiazoacetate, water, and the conjugated enone, Hu et al. discovered that addition of Brønsted acid, specifically 40 mol % of TsOH, remarkably improved the reaction efficiency of the catalytic system, providing much increased rate and selectivity of the reaction (from 75% yield, 90:10 dr, and 56% ee to 78% yield, 97:3 dr, and 96% ee). Although the role of the acid additive was not clearly studied, they speculated that the Brønsted acid activated the α,βunsaturated 2-acyl imidazole through H bonding to this substrate (Scheme 162).375 In the case of Pd-catalyzed asymmetric hydrogenation of unprotected indoles, Fan and Zhou et al. found that addition of Brønsted acid was essential for full conversion and high enantioselectivity (Table 52).376 The reaction did not occur Table 52. Hydrogenation of Unprotected Indole376

entry

additive

conversion (%)

ee (%)

1 2 3 4 5 6 7 8 9

TfOH PhSO3H TsOH·H2O TFA L-CSA D-CSA PhCO2H salicylic acid

95 >95 >95 >95 44 95%) was obtained, the yield of the product was rather low (99% conversion and 95% ee with similar regioselectivity. Scheme 174. Arylation of Allylic Amide397

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Scheme 175. Kinetic Resolution of rac-Aziridine398,399

Scheme 176. Isomerization of Epoxide400

Scheme 177. Amidation of Allylic Carbonate401−403

yield (Table 54).408 The absence of an additive led to a yield of 25%, whereas 56% yield was achieved with DMPU as an additive. Further screening showed that Hf(IV) gave a better yield of 60% than Zr(IV), and addition of extra 4 Å MS also greatly improved the yield to 80% with a slight improvement of enantioselectivity. It was proposed that the DMPU might serve two functions. It could (1) help the catalyst stay in its active monomeric form by inhibiting the formation of polymeric structure and (2) release the coordinated product from the metal and regenerate the catalyst.

Addition of DMPU was also beneficial for enantioselective cyanoamidation of olefins. Simple addition of DMPU led to an increase of the yield from 83% to quantitative and enantioselectivity from 74% to 81% (Scheme 181).409 4.2.4. Chiral Amines. Chiral amines, for example, chiral amino acid derivatives, could be used as highly efficient additive in metal-catalyzed asymmetric transformations. Usually these additives act as a base and a coligand in the reaction. Kumagai and Shibasaki et al. reported that α-amino acid esters, particularly H-D-Val-OtBu, as additive could significantly improve the reaction rate, yield, and enantioselectivity of 4077


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Review

Scheme 178. Intramolecular Allylic Amidation404

Table 53. Allylic Amination of N-Tosyl Propynylamine405

entry 1 2 3 4 5 6 7 8 9 10

additive

t (h)

yield (%)

major:minor

ee (%)

K2CO3 Cs2CO3 K2PO4 KOAc LiHMDS BSA TBD DBU DABCO

15 28 3 3 28 24 48 24 3 3

99% and ee of 91%. It should be noted that the use of antipode H-L-Val-OtBu led to inferior enantioselectivity of 80%, implying that the amine additive might be involved in the chiral transition state. On the basis of spectroscopic analyses and control experiments, they proposed that H-D-Val-OtBu worked

Scheme 180. Mannich-Type Reaction407

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Table 54. Epoxidation of Allylic Alcohol408

entry

metal

1 2 3 4

Zr(OtBu)4 Zr(OtBu)4 Hf(OtBu)4 Hf(OtBu)4

additive

yield (%)

ee (%)

DMPU DMPU DMPU + 4 Å MS

25 56 60 81

90 90 95 97

182).411 Without an additive, the reaction afforded the cyclopropanation/allylic alkylation product with a ratio of 65/ 35 and dr ratio of 5:1 of cyclopropanation. However, after addition of 1.0 equiv of LiCl, the ratio of cyclopropanation/ allylic alkylation could be increased to 80/20 together with an improvement of diastereoselectivity to 12:1. Addition of lithium halides as additives in the reaction was very crucial in the iridium-412 or rhodium-catalyzed413 allylic arylation using arylzinc nucleophiles. Take the iridium-catalyzed reaction for example; low conversion of 34% was observed without use of any additive, whereas full conversion with improved regioselectivity and enantioselectivity could be provided by adding lithium halides as additives. In particular, employment of LiBr led to the best results, giving complete conversion, with 72% yield, 66:34 regioselectivity, and 75% ee (Scheme 183). Zhou et al. disclosed that lithium fluoride significantly effected the enantioselective rhodium-catalyzed addition of arylboronic acids to α-ketoesters (Scheme 184).414 While only very low conversion could be attained without use of additive, an excellent yield of 96% and good ee of 77% were provided by using 2.0 equiv of LiF as an additive. It was proposed that LiF functioned as a Lewis base, promoting the transfer of the phenyl group of the phenylboronic acid to rhodium by binding to the boron atom and accelerating the reaction rate. Feng et al. investigated the electrophilic addition of αdiazoesters with ketones (Scheme 185).415 In the initial study, although an excellent enantioselectivity of 95% ee was obtained without any additive, the yield of alkylhydrazone product was rather low (21%). To improve the yield, they envisioned that the basic additives might be useful as they could improve the nucleophilic capability of ketone by the enolization. Keeping this in mind, they tried several basic salts and found that when using 10 mol % of Li2CO3 as a basic additive the yield could be greatly increased to 85% without any loss of enantioselectivity. In a [Ru(phgly)2(binap)]-catalyzed asymmetric hydrocyanation, Ohkuma et al. discovered that the introduction of lithium salts like LiCl,416 Li2CO3,417 or LiOC6H5418 as an additive to the catalytic system was highly crucial for the transformation. Take the hydrocyanation of α,β-unsaturated ketones for example; only 99 >99 >99 >99 >99 >99 >99 >99

0 58 79 52 70 35 89 91 80

bifunctionally: (1) as a coligand which coordinated to La3+ recognize/activate substrates and (2) as a base for deprotonation of ligand to facilitate the association of La3+ and the ligand. 4.3. Salts in Metal-Catalyzed Asymmetric Reactions

4.3.1. Lithium Salts. Lithium salts were screened as useful additives in metal-catalyzed asymmetric transformations. For instance, Hou et al. reported that lithium chloride played a crucial role on the selectivity in Pd-catalyzed cyclopropanation of acyclic amides with substituted allyl carbonates (Scheme 4079


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Scheme 182. Cyclopropanation of Acyclic Amide411

Scheme 183. Allylic Arylation412

Scheme 184. Addition of Arylboronic Acid to α-Ketoester414

Scheme 185. Addition of α-Diazoester with Ketone415

4.3.2. Sodium Salts. Sodium salts were frequently used as additives in catalytic asymmetric transformations. They usually acted as the anion counterpart or a base, sometimes involved in a heterobimetallic catalytic system. A more general and cheaper sodium salt, namely, NaCl, was developed as a useful additive by Yamamoto’s group for the promotion of tungsten-catalyzed asymmetric epoxidation of allylic alcohols with hydrogen peroxide (Scheme 188).420 They found that addition of LiF, Na2SO4, or NaCl could all improve the reaction yield and gave

Kumagai and Shibasaki et al. reported that addition of Li(OC6H4pOMe) as additive could completely alter the coppercatalyzed asymmetric Mannich-type reaction of thioamides (Scheme 187).419 While no reaction was observed without addition of Li(OC6H4pOMe), an excellent yield of 95% and enantioselectivity of 95% were attained by adding 10 mol % of Li(OC6H4pOMe) as an additive. It was speculated that Li(OC6H4pOMe) functioned as a hard Brønsted base to generate the active nucleophile from thioamide. 4080


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Scheme 186. Hydrocyanation416−418

Scheme 188. Epoxidation of Allylic Alcohol420

similar results. Due to its cheap property, they chose NaCl for further optimization. The employment of 0.5 equiv of NaCl additive improved the reaction yield (92% vs 84%) while maintaining the excellent enantioselectivity. The role of the additive in this transformation was defined as an inhibitor of a ring-opening side reaction, which decreased the yield of the reaction. Addition of NaI was able to increase the reactivity of nickelcatalyzed reductive cross-coupling of styrenyl bromides and benzyl chlorides (Table 56).421 In the initial model reaction without an additive, the reaction gave cross-coupling product (CP) in 56% yield and 87% ee, together with the homocoupling product (HP) in 20% yield. Addition of NaI or TBAI could increase the yield of CP and decrease the yield of HP. In the presence of NaI, lowering the reaction temperature could significantly improve the yield of CP to 93% and ee to 93%, meanwhile reducing the yield of HP to 8%. The beneficial effects of NaI might be attributed to the in-situ formation of organoiodide electrophiles or acceleration of electron transfer between Mn and Ni. Matsunaga and Shibasaki reported that NaI could be used as an efficacious additive in catalytic asymmetric cyclopropanation of enones with dimethyloxosulfonium methylide (Scheme 189).422 Whereas only 6% of ee was obtained without the use of any additive, a greatly improved enantioselectivity of 55% ee could be furnished by adding 10 mol % of NaI additive. Furthermore, use of molecular sieves as coadditive provided 82% enantioselectivity. On the basis of the control experiments and the previous studies,423 they speculated that after addition of NaI, an alkali metal exchange would occur to afford a La−

Li2−Na−L3 complex, which would slightly modify the asymmetric environment, thereby leading to better results. Hamada disclosed that 1.0 equiv of sodium acetate NaOAc dramatically affected the reaction rate and enantioselectivity of Ir-BINAP-catalyzed hydrogenation of the α-amino-β-keto ester (Scheme 190).424 The employment of NaOAc as additive greatly shortened the reaction time from 48 to 3 h and increased the enantioselectivity from 27% ee to 69% ee. In particular, further introduction of 0.06 equiv of NaI as a cooperative additive could improve the enantioselectivity to 90% ee with good yield (82%) and excellent diastereoselectivity (>99:1). The same group further discovered that addition of NaBArF as additive could promote the reaction to 100% yield, albeit with similar enantioselectivity (Scheme 191).425 Interestingly, the enantioselectivity could be increased when the hydrogen pressure was reduced from 100 to 4.5 atm, providing an enantiomeric excess of 93%. The role of additive was proposed to act as a counteranion provider for in-situ generation of the catalytic species I. Feng et al. developed a chiral Sc(III)−N,N′-dioxide complexcatalyzed enantioselective fluorination of N-unprotected 3substituted 2-oxindoles in which basic additive played a crucial role (Scheme 192).426 Whereas no reaction was observed without use of any additive, good yield (79%) and excellent ee (97%) were provided by using 50 mol % of Na2CO3 as additive. Increasing the amount of additive to 120 mol % could further improve the yield to 95% without any loss of enantioselectivity. It was considered that the base additive was used to accelerate the enolization of oxindole and prompted the transformation. Nishiyama et al. reported that addition of 5 mol % of NaOtBu could greatly accelerate the asymmetric catalytic diboration of terminal alkene (Scheme 193).427 While only a low yield of 20% and moderate ee of 66% were attained without additive, an excellent yield of 94% and ee of >99% were provided by the use of NaOtBu additive. It was proposed that

Scheme 187. Mannich-Type Reaction of Thioamide419

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Table 56. Reductive Cross-Coupling421

entry 1 2 3 4

additive

temp (°C)

yield HP (%)

yield CP (%)

ee CP (%)

NaI TBAI NaI

20 20 20 0

20 17 13 8

56 67 64 93

87 87 91 93

Scheme 189. Cyclopropanation of Enone422

Scheme 190. Hydrogenation of the α-Amino-β-Keto Ester424

Scheme 192. Fluorination of Oxindole426

Kobayashi et al. investigated the additive effect of a catalytic asymmetric Mannich-type reaction of α-hydrazono ester with silicon enolates in aqueous media activated by ZnF2 (Scheme 194).428 When no additive was used, only a low yield of 21% was observed with good enantioselectivity of 90% ee. Introduction of 1 mol % of TfOH as an additive could improve the yield of the reaction. However, no marked effect was observed by using other acidic additive, and the reactions utilizing metal triflates as additives produced better yields. In particular, alkali metal triflates produced higher yields than TfOH, and the best yield was obtained when NaOTf was employed. The results indicated that TfOH acted not as a protic acid but as a triflate anion counterpart. 4.3.3. Potassium Salts. Katsuki et al. showed that basic additive could enhance aluminum−salalen catalytic enantioselective hydrophosphonylation of aldehydes (Scheme 195). In the absence of basic additive, the reaction proceeded quite slowly with a high catalyst loading of 10 mol %.429 Alkali metal carbonate like K2CO3 made the yield of the transformation perfect (>99% vs 87%) with low catalyst loading of 2 mol %. In the process, base was considered to break the balance of phosphonate−phosphite tautomerization and deprotonate

Scheme 191. Hydrogenation of the α-Amino-β-keto Ester425

NaOtBu could (1) work with the catalyst [Rh(phebox)] to generate the active tBuO−RhIIIL* I and (2) accelerate the diboration as the formed tBuO−Bpin II was involved in the catalytic cycle of metathesis or transmetallation. 4082


Chemical Reviews

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Scheme 193. Diboration of Terminal Alkene427

Scheme 194. Mannich-Type Reaction of α-Hydrazono Ester428

phosphonate to form the active phosphite, thereby leading to the improved reactivity.430 Zhang et al. reported a Rh-complex-catalyzed asymmetric hydrogenation of α-primary and secondary amino ketones in which the effect of the base additives was examined (Scheme 196).431 The results revealed that inorganic bases with suitable pKa could improve both the yield and the enantioselectivity. Without any additive, the reaction proceeded in 90% yield and 54% ee. Introduction of 10 mol of % K2CO3 additive increased the yield to >95% and enantioselectivity to 90% ee. Increasing the amount of K2CO3 additive to 50 mol % could further improve the enantioselectivity to 95%. Other bases like NaHCO3 and KHCO3 could also give good results but with a slightly lower ee. K2CO3 was also of high efficiency in copper-catalyzed enantioselective 1,3-dipolar cycloaddition of azomethine ylides with alkylidene malonates (Scheme 197). Although only a trace amount of adduct could be observed in the absence of basic additives, an excellent yield of 92% and satisfactory ee of 75% were achieved when 2 equiv of K2CO3 additive was added to the catalytic system.432 K3PO4 could be also used as a basic additive in asymmetric catalytic reactions. Hartwig et al. reported that the correct choice of base was necessary for high conversion and selectivity in the N-allylations of benzimidazoles (Scheme 198).433 No reaction occurred in the absence of a base. K3PO4 or Na3PO4 gave the branched product in high yield and selectivity, while other bases like Li3PO4, KOtBu, or NaOtBu gave either poor

Scheme 195. Hydrophosphonylation of Aldehyde429,430

Scheme 196. Hydrogenation of Amino Ketone431

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Scheme 197. 1,3-Dipolar Cycloaddition432

Scheme 198. N-Allylation of Benzimidazole433

Scheme 199. Addition of Boronic Acid to Imine435

Scheme 200. Addition of Boronic Acid to Nitroalkene436

significantly accelerate addition of arylboronic acids to aliphatic imines (Scheme 199).435 In a rhodium-catalyzed asymmetric conjugate addition of organoboronic acids to nitroalkenes, Xu and Lin et al. discovered that KHF2 was greatly beneficial to the reaction rate and yield of the transformation (Scheme 200).436 While only 60% of the yield could be obtained in 19 h without KHF2 in the process, 98% yield was achieved by adding 3 equiv of KHF2 additive, with a slight increase of the enantioselectivity.

conversion or poor selectivity. In the presence of K3PO4, the best results were obtained, affording the desired product in 92% yield and 97% ee. In the Rh-catalyzed addition reactions of arylboronic acids, addition of basic additive could promote the formation of LRhOH, which was an active intermediate for transmetalation with arylboronic acids.434 Ellman et al. found that the employment of 20 mol % of K3PO4 as an additive could 4084


Chemical Reviews

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Scheme 203. Negishi Reaction440

Addition of KHF2 could react with boronic acids to generate potassium organotrifluoroborates, which were involved in the transmetalation with rhodium. 4.3.4. Cesium Salts. Cesium carbonate was found as the most suitable basic additive in iridium-catalyzed highly enantioselective hydrogenation of α-substituted α,β-unsaturated carboxylic acids by Zhou et al. (Scheme 201).437,438 In the Scheme 201. Hydrogenation of Unsaturated Carboxylic Acid437,438

as an additive.441 As shown in Scheme 204, the reaction would not occur without use of silver additive, while good yield and excellent enantioselectivity could be magically attained by adding 5 mol % silver salt as an additive. Furthermore, different silver salts affected the transformation diversely, and AgSbF6 was optimized as the best candidate. The role of this additive was interpreted as halogen scavenger and as counteranion provider that benefited generation of a catalytically active cationic rhodium species. Similarly, in the case of rhodium-catalyzed [2 + 2 + 2] carbocyclization reactions of 1,6-enynes with methyl arylpropiolates, Evans et al. found that the reactivity could be dramatically affected by adjusting the nature of the counterion (Scheme 205).442,443 They tested several silver salts and found that AgBF4 was the best additive. By using AgBF4 as an additive and (S)-Xyl-P-PHOS as a ligand, excellent yield, regioselectivity, and enantioselectivity were achieved. Zezschwitz et al. discovered that silver salts additive greatly effected the conversion and yield of the enantioselective Rh(I)/ binap-catalyzed 1,2-addition of AlMe3 to cyclic enones (Scheme 206).444 Whereas only moderate yield (64%) was attained without use of any additive, a high yield of 88% while retaining enantioselectivity was provided by adding AgBF4 in the reaction. They suggested that in the absence of an additive, the major phosphorous species was the dimeric complex [{Rh(binap)Cl}2], which could slowly liberate the catalytically active species. However, addition of AgBF4 could promote cleavage of this dimer, thus giving a more active catalyst. Hsung et al. reported that AgSbF6 as an additive could lead to nearly perfect transformation for chiral copper-catalyzed enantioselective [4 + 3] cycloaddition of nitrogen-stabilized oxyallyl cations derived from allenamides (Scheme 207).445 Although good enantioselectivity (92% ee) could be obtained without use of AgSbF6 additive, it was not sufficient enough for further use as a pharmaceutical intermediate. Perfect enantioselectivity (99% ee) could be achieved by using AgSbF6 additive. In a chiral Ru-complex-catalyzed asymmetric transfer hydrogenation of cyclic imines or iminium salts446,447 it was found that silver salts played a significant additive role in the transformation. For instance, when polycyclic iminium was used as starting material, only trace reaction was observed

case of α-aryloxy-unsaturated carboxylic acids, the reaction could hardly occur in the absence of additives, but full conversion and optically pure product could be obtained by adding 0.5 equiv of Cs2CO3 as an additive.437 They speculated that addition of basic additive formed the carboxy anion, which was beneficial to chelation of the substrate and the iridium center of catalyst, and thereby prompted the reaction with high efficiency and selectivity. In the copper-catalyzed asymmetric endo-selective [3 + 2] cycloaddition of imino esters with nitroalkenes, Arai et al. observed that the basic additives played a remarkable role on the reactivity and selectivity (Scheme 202).439 In the absence of an additive, the reaction afforded the product in rather low yield (18%) and selectivity (endo:exo 83:17 and 51% ee). With the assistance of a base like Cs2CO3, the yield was greatly increased to 96%, the ratio of endo:exo to 99:1, and ee to 99%. Fu et al. reported that cesium iodide as an additive could significantly improve the yield of Ni-catalytic enantioselective Negishi reactions of racemic benzylic bromides with achiral alkylzinc reagents (Scheme 203).440 Using 1.2 equiv of CsI in the reaction could improve the yield from moderate (69%) to excellent (91%) while retaining the enantioselectivity. It was proposed that CsI was involved the in-situ formation of a benzylic iodide and generation of reactive zincate complexes. 4.3.5. Silver Salts. Silver salts can be used as efficient additives in metal-catalyzed asymmetric reactions. They often not only function as the halogen scavenger or as a counteranion provider for the in-situ generation of active catalytic species but also act as a Lewis acid for the promotion of the reaction. For instance, Gandon and Aubert et al. represented a highly enantioselective rhodium-catalyzed [2 + 2 + 2] cycloaddition of diynes to sulfonimines in which silver salt played a decisive role Scheme 202. [3 + 2] Cycloaddition439

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Scheme 204. [2 + 2 + 2] Cycloaddition of Diyne441

Scheme 205. [2 + 2 + 2] Carbocyclization of 1,6-Enyne442,443

Scheme 206. Addition of AlMe3 to Cyclic Enone444

Scheme 208. Transfer Hydrogenation446,447

without use of additive, while a moderate yield and good enantioselectivity were obtained with the help of AgSbF6 additive (Scheme 208). It was demonstrated that the anion of the silver salt acted as halogen scavenger and as counteranion provider for in-situ generation of active catalytic species.447 A more remarkable additive effect of silver salts was observed by Dong et al. in rhodium-catalyzed ketone hydroacylation for the synthesis of phthalides (Table 57).448 In the process they discovered that silver salts acted as counteranion provider to influence the reaction results. As shown in Table 57, counterions with various coordinating strengths (SbF6 < BF4 < −OTf < NO3 < Cl) played crucial roles in the reaction rate, yield, and enantioselectivity. More strongly coordinating counterions gave better selectivity for both enantioselectivity and chemoselectivity for hydroacylation over decarbonylation. AgNO3 was the optimal additive as nitrate is less strongly coordinating than chloride (giving shorter reaction time) but coordinating enough to suppress decarbonylation and assist in enantioinduction.

Gade et al. represented an enantioselective iron-catalyzed azidation of β-keto esters and oxindoles in which silver carboxylate additive played a crucial role (Scheme 209).449 Inspired by the observation that iron(II) carboxylates gave rise to the highest enantioselectivities, they examined the effect of various carboxylate counterions provided by silver carboxylate additives for the in-situ generation of active catalytic species in the reaction. The results exhibited that silver 4-nitrobenzoate gave the highest reaction rate (48 vs 72 h), yield (87% vs 61%), and enantioselectivity (93% ee vs 66% ee). 4.3.6. Ammonium Salts. Ammonium salts were also one of the important subclasses of salt additives. Trost and coworkers developed a Pd-catalyzed asymmetric addition of oxindoles and allenes (Scheme 210).450,451 In this study, due to the lower acidity of oxindoles, addition of acid would facilitate

Scheme 207. [4 + 3] Cycloaddition445

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Table 57. Synthesis of Phthalide448

entry

X

t (h)

yield P1 (%)

ee P1 (%)

yield P2 (%)

1 2 3 4 5 6

SbF6 BF4 OTf OMs NO3 Cl

24 24 0.5 10 7 72

30 76 >95 >95 >95 92

40 29 81 91 97 97

52 24 20:1 10:1 13:1 >20:1 10:1 >20:1 >20:1 >20:1

80 67 71 73 72 87 85 94

90 91

>20:1 >20:1

89 76

recognized by Shibasaki and co-workers in the asymmetric azaMorita−Baylis−Hillman reaction of imine with methyl acrylate (Scheme 240).509 In their initial study, the reaction gave a promising enantioselectivity of 88% but with a low yield of 46% in the presence of 10 mol % of ligand and La(OiPr)3. When increasing the amount of ligand to 15 mol % while maintaining the amount of La(OiPr)3 at 10 mol %, the yield could greatly increase to 90% with almost the same ee, suggesting that the excess ligand worked not as a ligand but as a proton source to accelerate the reaction.510 Therefore, they investigated some phenolic additives. Gratifyingly, introduction of 10 mol % of 4,4′-thiobis(6-tBu-m-cresol) could dramatically improve the yield of the reaction from 46% to 96%, with slight improvement of enantioselectivity. The role of the phenol additive was not clearly investigated; however, it was speculated that it acted as a 4097


Chemical Reviews

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Scheme 242. Suzuki−Miyaura Cross-Coupling518,519

enantioselectivity of the reaction from 80% to 94%.517 The role of 4-tBuC6H4OH was investigated, and the results showed that it would act as a ligand to samarium and dissociate the higher order oligomer species, which were less enantioselective for the present reaction, to form more enantioselective μ-oxo-μ-aryloxy trimer (or hexamer) as a major species (Table 60). Ohmura and co-workers reported that the configuration of the Suzuki−Miyaura cross-coupling product could be switched by the right choice of a Brønsted or Lewis acid additive (Scheme 242).518,519 In the presence of a Brønsted acid like PhOH additive, the inverting C−C bond coupling took place to afford the (S)-product in 96% es with the inversion of configuration. In contract, the Lewis acid Zr(OiPr)4·iPrOH led to the (R)-product in 83% es with the retention of configuration. In the absence of any additive, the boronic esters exist the intramolecular coordination between the amide oxygen and the boron atoms. Addition of PhOH could reinforce this interaction; thus, the electrophilic attack could only start from the opposite side of the boron atom, affording the inverse product. Addition of Zr(OiPr)4·iPrOH could disrupt the interaction of boronic esters by the competitive coordination to the oxygen atom to afford the tricoordinated boron, which facilitates the formation of a cyclic fourmembered-ring transition state in which the electrophilic attack could take place at the same side of boron atom, affording the retention product.

proton source to accelerate the proton transfer step, which accelerated the deprotonation of the α-proton by a Brønsted basic La catalyst. They also found that protic phenolic additives played a crucial role in Gd-complex-catalyzed enantioselective addition of cyanide to ketoimines,511−513 enones,514 and α,β-unsaturated N-acylpyrroles.515 Take the Strecker reaction of ketoimine for example (Table 59); the reaction proceeded slowly for 14 h to give the product in quantitative yield but with a rather low ee of 33% when using 10 mol % of catalyst without an additive. After addition of additives like alcohols or phenols, the reaction time was significantly reduced and the enantioselectivity improved, even with 5 mol % of catalyst. When 10 mol % of 2,6dimethylphenol (DMP) was used, the reaction time could be reduced to 2 h with an improved enantioselectivity to 99%.511 On the basis of the ESI-MS studies of the active catalyst, they suggested that the additive might change the active catalyst structure.511,512 In the presence of Gd(OiPr)3 and ligand in a 1:2 ratio and TMSCN, double-silylated complex I was formed first. After addition of DMP, it changed the catalyst structure from the O-silylated form I to the O-protonated form II, which showed higher reactivity and selectivity toward this reaction. The same group further disclosed that substituted phenol could significantly improve the enantioselectivity of chiral copper complex-catalyzed aldol reaction of ynones and aldehyde (Scheme 241).516 By adding 0.4 equiv of pMeOC6H4OH, the enantioselectivity of the reaction was increased from 30% to 86% with slightly improved yield to 88%. Inspired by this result, a series of phenol and alcohols was screened, and it was found that CF3CH2OH (TFE) gave the best results of 96% yield and 88% ee. Addition of protic additive was thought to suppress the retro-aldol reaction. In a chiral heterobimetallic transition metal/rare earth metal system catalytic asymmetric nitro-Mannich reaction, Matsunaga and Shibasaki et al. disclosed that employment of 10 mol % of 4-tBuC6H4OH as an additive lead to a significant increase of the

4.5. Phosphanes, Phosphane Oxides or Phosphoramidates

4.5.1. Phosphanes. chiral phosphines were found to dramatically enhance the rate and enantioselectivity of Rh/ phosphoramidite-catalyzed hydrogenation of α,β-disubstituted unsaturated acids by Feringa and co-workers (Table 61).520 Initially they discovered that the introduction of PPh3 to catalytic system gave a drastic improvement of reaction conversion from 34% to 100% and enantioselectivity from 16% to 88% compared to those using chiral phosphoramidite monodentate ligands alone. Further screening of various 4098


Chemical Reviews

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Table 61. Hydrogenation of Unsaturated Acid520

entry 1 2 3 4 5 6 7 8 9 10 11 12

R

ee (%)

TOF

Ph o-tolyl m-tolyl p-tolyl xylyl mesityl m-ClPh p-ClPh Cy n Bu t Bu

16 88 97 87 86 89 33 89 90 87 67 13

2 46 33 69 61 92 3 46 18 28 17 2

improved the yield to 82% without any loss of enantioselectivity. The role of Ph3P in this transformation was considered as a coligand which would occupy free coordination sites of rhodium catalyst, preventing the interaction of AgBF4 with rhodium. 4.5.2. Phosphane Oxides. Achiral phosphane oxides can be also used as efficient additives in catalytic asymmetric transformations, and pronounced ligand effects can be observed. In a catalytic asymmetric cyano-ethoxycarbonylation reaction of aldehydes using a YLi3tris(binaphthoxide) (YLB) complex, Matsunaga and Shibasaki et al. discovered that additives had a key role in promoting the reaction (Table 62).524,525 When no additive was used, the reaction could not proceed in 7.5 h, while 93% yield and 64% ee were obtained by adding 10 mol % of Ph3P(O) as an additive in 8.5 h. When adding 10 mol % of Ph3P(O) and 10 mol % of H2O as additives simultaneously, 88% yield and 83% ee could be provided in 2.5 h. After further optimization, 10 mol % of tris(2,6dimethoxyphenyl)phosphine oxide and 30 mol % of H2O as additives furnished the best reaction rate and enantioselectivity, with 97% yield and 92% ee in 1.5 h. The detailed mechanism of additives was not clear; however, a possible active species was postulated, which might interpret their role. The same group further disclosed that addition of phosphine oxides was highly effective in improving the efficiency of chiral lanthanum complex-catalyzed asymmetric Corey−Chaykovsky epoxidation reaction of ketones (Table 63).526 An 80% yield and 72% ee were obtained without any phosphine oxide additive. After careful screening of phosphine oxide additives, 98% yield and 96% ee could be furnished when using 2,4,6trimethoxyphenyl phosphine oxide as additive. The results exhibited that the electron-donating and coordinating MeO substituents at the 2,6-positions were prone to improving enantioselectivity. 31P NMR analysis of 2,4,6-trimethoxyphenyl phosphine oxide alone (3.50 ppm) and 2,4,6-trimethoxyphenyl phosphine oxide with LLB (16.3 ppm) indicated that 2,4,6trimethoxyphenyl phosphine oxide coordinates to LLB. It was speculated that the LLB:Ar3P(O) =1:1 complex would be the active species in the catalytic system. Electron-rich and bulky achiral additive would suitably modify the chiral environment of LLB, resulting in better yield and enantioselectivity. By using similar strategy, the catalytic asymmetric epoxidations,527,528 addition of allyl cyanide to ketones,529 and aldol reaction of thioamides530 could be greatly improved. 4.5.3. Phosphoramidates. Hoveyda et al. reported an impressive finding that phosphoramidates could give rise to improved results in the alkylation of ketoesters531 or alkynyl ketones (Scheme 245).532 In the absence of an additive, the

phosphines showed that substitution at the ortho position of triphenylphosphine increased the ee value significantly, whereas substitution at the meta or para position had hardly any influence on the enantioselectivity. On the basis of preliminary NMR experiments the positive additive effect was attributed to the formation of a heterocomplex comprising one chiral phosphoramidite and one achiral phosphine bound to the Rh center, which was the predominant factor for the remarkable selectivity enhancement and high activity. Similarly, Ding et al. developed a highly versatile and enantioselective Rh-catalyzed asymmetric hydrogenation of β,βdiarylacrylic acids in which triphenylphosphine exhibited a highly efficient additive effect (Scheme 243). Introduction of 1 mol % of PPh3 additive increased the conversion from 15% to >99% and ee from 38% to 95%.521 It was proposed that the additive functioned as a coligand in the process. This catalytic system was also effective for asymmetric hydrogenation of αCF3- or β-CF3-substituted acrylic acids.522 Tanaka et al. described an asymmetric cascade reaction of 2alkynylbenzaldehydes with isatin catalyzed cooperatively by cationic rhodium(I) and silver(I) complexes in which PPh3 additive played a crucial role (Scheme 244).523 They found that addition of 10 mol % of Ph3P could dramatically promote the conversion of the reaction from 30% to full with the yield from 6% to 53%. Decreasing the amount of Ph3P to 5 mol % further Scheme 243. Hydrogenation of β,β-Diarylacrylic Acid521

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Scheme 244. Reaction of 2-Alkynylbenzaldehyde with Isatin523

additive in the process (Scheme 246).533 Compared to the low enantioselectivity of 50% obtained without any additive, a good enantioselectivity of 89% could be furnished when 10 mol % of diethyl phosphoramidate was added as additive. Further optimization revealed that 30 mol % of diethyl phosphoramidate provided the best results, with 92% yield, >99:1 dr, and 95% ee. With regard to the mechanism, it was speculated that the cross-binding of 5H-oxazol-4-one to the two zinc centers was not conducive to the final enantioselectivity, while the deprotonated diethyl phosphoramidate could covalently bind to the two zinc atoms tightly, which could inhibit the crossbinding, thus leading to higher selectivity.

Table 62. Cyano-Ethoxycarbonylation Reaction524,525

entry additive 1 (mol %) additive 2 (mol %) 1 2 3 4 5 6

PO1 (10) H2O H2O H2O H2O

PO1 (10) PO1 (10) PO2 (10)

(10) (10) (30) (30)

t (h)

yield (%)

ee (%)

7.5 8.5 9 2.5 2.5 1.5

0 93 84 88 54 97

64 58 83 89 92

4.6. Halides in Metal-Catalyzed Asymmetric Reactions

It was found that iodine could be used as an additive in asymmetric hydrogenation reactions. Zhang et al. found that addition of I2 could increase the enantioselectivity of iridiumcatalyzed asymmetric hydrogenation of arylimines534 or aryl ketones (Scheme 247).535 In the absence of an additive, the hydrogenation of imine afforded the product in 77% ee, while addition of 10 mol % of I2 greatly improved the ee to 94%. They suggested that the oxidative addition of I2 to the IrI precursor I generated the IrIII species, and subsequent heterolytic cleavage afforded the LIrIII−H species II, which was the active catalyst. Similarly, in the asymmetric hydrogenation of quinolones, introduction of 10 mol % of I2 could dramatically improve the reaction yield and enantioselectivity from trace yield and low ee to >95% and 94% ee (Scheme 248).536 To further demonstrate the role of iodine additive, a wide variety of halide additives were tested. It suggested that TCIA, IBr, ICl, BCDMH, and DCDMH as the additives could also give almost full conversion and good enantioselectivity. Control experiments revealed that chloride and iodide were crucial for the reactivity and enantioselectivity, and the iodine activated the catalyst in the hydrogenation of quinolines.537 Subsequently, they used this strategy in the enantioselective hydrogenation of 3,4disubstituted isoquinolines. In this case, the use of 1-bromo3-chloro-5,5-dimethyl-hydantoin (BCDMH) as additive gave slightly superior enantioselectivity with the full conversion of the substrate.538 Similarly, Chan and co-workers disclosed that the employment of 2 mol % of I2 as an additive significantly improved both the reaction conversion and the enantioselectivity in the asymmetric hydrogenation of quinoxalines (Scheme 249).539 Iodide was found to be highly effective in asymmetric hydrogenation of enamines as well (Scheme 250).540,541 Zhou et al. discovered that the use of 2 mol % of I2 as additive

Table 63. Corey−Chaykovsky Epoxidation526

entry 1 2 3 4 5 6 7 8 9

R

yield (%)

ee (%)

Ph p-ClPh C6F5 n Bu Cy 2,4,6-Me3Ph 2,6-MeO2Ph 2,4,6-MeO3Ph

80 77 99 61 87 99 97 84 98

72 80 74 48 75 76 75 93 96

reaction afforded the product in 90% conversion and 67% ee. However, after addition of diethyl phosphoramidate, the enantioselectivity was noticeably improved to 95%. The use of dimethylphosphoramidate gave negative effects, suggesting that the acidic protons (NH2) were critical to the effectiveness of the additive. The deprotonated diethyl phosphoramidate could (1) activate alkylzinc reagent intramolecularly and (2) direct the dialkylzinc reagent toward addition to the ketoester. In a catalytic asymmetric Mannich reaction of 5H-oxazol-4ones for the synthesis of α-alkyl norstatine derivatives by Wang et al., diethyl phosphoramidate was realized as an effective 4100


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Scheme 245. Alkylation of Ketoesters531

Scheme 246. Mannich Reaction of 5H-Oxazol-4-one533

4.7. Others

dramatically increased the enantioselectivity from 14% ee to 83% ee. Furthermore, when 20 mol % of acetic acid, which strongly lowered the reaction conversion alone, was added as a cooperative additive to the catalytic system, the reaction time was remarkably shortened (12 vs 48 h) with a slight improvement of enantioselectivity. In particular, addition of I2 and acetic acid brought a more significant improvement so that the hydrogenation could proceed under a much lower pressure of H2. It was found that iodide additive was also significantly effective in iridium-catalyzed asymmetric hydrogenation of cyclic enamines.

4.7.1. Aldehydes. In a chiral Sc-complex-catalyzed asymmetric Povarov reaction, Feng et al. discovered that aldehyde could be used as additive for the improvement of the yield of the reaction (Scheme 251).542 Whereas a low yield of 39% was obtained without any additive, an increased yield 58% was provided after adding 0.5 equiv of corresponding aldehyde as an additive. Further introduction of MgSO4 could furnish satisfactory yield without any loss of the enantioselectivity of the reaction. The role of aldehyde in this process was considered to act as inhibitor of decomposition of imine. 4.7.2. Amino Alcohols. In the asymmetric alkylation of pyrimidine-5-carbaldehyde using β-amino alcohol as a ligand, 4101


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Scheme 247. Hydrogenation of Arylimine534

Scheme 248. Hydrogenation of Quinolone536

Scheme 249. Hydrogenation of Quinoxaline539

Scheme 250. Hydrogenation of Enamine540,541

Soai and co-workers found that addition of an achiral amino alcohol could reverse the configuration of the product (Scheme 252). In the absence of an additive, the reaction affords the product in >98% ee with R configuration, while addition of an achiral amino alcohol led to the reverse configuration of S.543 A subsequent mechanism study revealed that chiral and achiral amino alcohol interact with each other with zinc alkoxides to form a catalytically active chiral heterodinuclear aggregate, which could promote the formation of the opposite enantiomer.544,545 Using the same model reaction, they found that phenol additives could also reverse the configuration when using diol as the ligand.546

4.7.3. B(OMe)3 or BPh3. Uang and co-workers demonstrated that addition of B(OMe)3 could increase the yield and enantioselectivity in the asymmetric addition of dimethylzinc to α-ketoesters (Table 64). In the absence of an additive, the reaction proceeded in 65 h to give the product in 78% yield and 61% ee. In order to improve the enantioselectivity they tested some additives. DiMPEG547 and 2-propanol,548 which were positive in parallel reactions, even gave lower enantioselectivity. Interestingly, addition of 25 mol % of B(OMe)3 significantly reduced the reaction time to 20 h with an improved yield to 4102


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Scheme 251. Povarov Reaction542

Scheme 252. Alkylation of Pyrimidine-5-carbaldehyde544,545

Table 64. Addition of Dimethylzinc to α-Ketoester549

entry 1 2 3 4 5 6

Scheme 253. Intramolecular Arylcyanation of Unactivated Olefin550

additive (mol %)

t (h)

yield (%)

ee (%)

DiMPEG (10) 2-propanol (25) B(OMe)3 (25) B(OMe)3 (50) B(OMe)3 (100)

65 45 20 20 20 20

78 18 65 90 74 78

61 27 59 71 63 60

90% and ee to 71%. Further increasing the amount of B(OMe)3 did not have any positive effects.549 Jacobsen et al. found that a Lewis acid additive like BPh3 could significantly accelerate intramolecular arylcyanation of unactivated olefins (Scheme 253). After the systematic investigation of solvent, ligand, and Lewis acid additive, the corresponding product indane could be obtained in 81% yield and 95% ee.550 The observed positive effects might be derived from the coordination of the cyano group to the Lewis BPh3 through the enantioselectivity-determining step.551 4.7.4. (Boc)2O. In the asymmetric hydrogenation of βdehydroamino acid derivatives, a challenging problem is product inhibition. Hansen and Rosner elegantly solved this problem by the in-situ Boc protection of the amine product (Table 65).552 In the initial reaction without adding any additives the TOF at 50% conversion was 220. As expected, a significant reduction in the TOF50% was observed even in prolonged reaction time when the same reduction was conducted in an initial charge of product. In order to avoid product inhibition, the authors tried adding some acylating agents like acetic anhydride, benzoyl chloride, and benzoic

Table 65. Hydrogenation of β-Dehydroamino Acid552

4103

entry

cat. loading (mol %)

1 2 3

1.0 1.0 0.2

additive (equiv)

t (h)

TOF50%

product (X = H) (0.31) (Boc)2O (2.0)

3.6 11.3 1.1

220 50 950


Chemical Reviews

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Scheme 254. Hydrogenation of Ketimine553−555

ether simultaneously. Gratifyingly, the desired product could be obtained in 90% yield with 96% ee when using 1.0 equiv of KF and 18-crown-6. Using a similar strategy, the reaction of allylic carbonates with enol silanes from vinylogous esters or amides could also be promoted significantly (Scheme 256).559 About the mechanism, it was suggested that the additives were not used to activate the enol silanes but served as a base to promote the cyclometalation to generate the active Ir catalyst. Evans and co-workers found addition of 15-crown-5 had positive effects on the enantioselectivity in the rhodiumcatalyzed allylic substitution using the benzyl nitrile (Scheme 257).560 Simple addition of 15-crown-5 led to an increase of enantioselectivity from 72% to 84%. Using rhodium(I) catalyst Rh(cod)2OTf instead of RhCl(PPh3)3, the ee could be further improved to 92%. In this reaction, 15-crown-5 might be used as a deaggregating agent to affect the equilibrium between C- and N-metalated forms. 4.7.7. Dibenzylideneacetone. In the 1,1-arylborylation of alkenes using a chiral anion phase-transfer strategy, Toste et al. found that addition of exogenous dibenzylideneacetone (dba) additive could promote the reaction as it could increase the yield from 26% to 39% with a slight loss of enantioselectivity. Though they did not observe direct ligand exchange of Pd2(dba)3, they proposed the dba additive could stabilize the Pd species along the catalytic cycle (Scheme 258).561 4.7.8. Methyl Benzoate. Davies et al. reported an interesting finding that methyl benzoate could noticeably promote dirhodium-catalyzed cyclopropanations (Scheme 259). Simple addition of methyl benzoate led to a reduction of reaction time from 42 to 28 h and an increase of enantioselectivity from 65% to 83%.562 Tetramethyl urea563 or OP(Oct)3,564 which was positive in parallel reactions, afforded even results here. Although the actual role of methyl benzoate was unclear, they proposed that it might stabilize the rhodium carbenoid species by coordination to the carbenoid or the other rhodium center. 4.7.9. Styrene. Alexakis et al. presented an interesting observation that styrene could be employed as a highly efficient additive in asymmetric conjugate addition of dialkyl zinc to αhalo enones.565 As shown in Scheme 260, the use of styrene could dramatically improve the enantioselectivities of both enantiomers. The role of styrene in this reaction was mainly viewed as a radical scavenger. On one hand, π coordination of Cu to the double bond of styrene resulted in a favorable modification of the environment of the catalytic organometallic species; on the other hand, styrene may inhibit nonasymmetric conjugate addition by trapping the initial Et radical. 4.7.10. TMSCl. It has been reported that TMSX reagents could accelerate the rate of metal-catalyzed reactions by

anhydride, but they all led to the acylation or decomposition of the enamine substrate. Gratifyingly, addition of (Boc)2O to the reaction had a favorable effect on the TOF50%, as it could react very slowly with enamine substrate but quickly with amine product. With (Boc)2O, the TOF50% was significantly increased to 950 in reduced catalyst loading and reaction time. By using a similar product inhibition strategy, the hydrogenation of N-alkyl, alkyl and aryl ketimines, and cyclic N-alkyl imines could be improved considerably (Scheme 254).553−555 Take the hydrogenation of N-benzylimine of acetophenone for example; in the absence of an additive, the reaction was sluggish (30% conversion) and gave some decomposed products. However, adding 1.1 equiv of (Boc)2O significantly improved the reaction, affording the corresponding product in full conversion and 86% ee. 4.7.5. Cobalt Complex. Yamamoto et al. showed a chiral chromium complex-catalyzed asymmetric Nozaki−Hiyama propargylation of aldehydes whose enantioselectivity was greatly enhanced by cobalt complex (Scheme 255).556 By Scheme 255. Nozaki−Hiyama Propargylation556

adding 1 mol % of coadditive to the catalytic system, the enantioselectivity was improved from 80% to 92% ee. By the CoI/CoII/CoIII cycle, the coadditive was able to accelerate the initial formation of alkyl radicals, which were then captured by chiral chromium species, thus leading to the improvement of enantioselectivity. 4.7.6. Crown Ethers. A pronounced additive effect on the reactivity was observed by Hartwig in the asymmetric allylic substitution of allylic carbonates with silyl enolates (Table 66).557,558 The reaction did not give any product with KF or ZnF2 as the additive. The use of soluble fluoride salts like TASF or TBAT only resulted in the decomposition of the substrates. Considering that crown ethers have strong binding ability for alkali metal ions, they tried to add the fluoride salt and crown 4104


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Table 66. Allylic Substitution with Silyl Enolate557,558

entry

additive 1 (equiv)

1 2 3 4 5 6 7

KF (1.0) ZnF2 (0.5) CsF (1.0) TASF (1.0) TBAT (1.0) CsF (1.0) KF (1.0)

additive 2 (equiv)

yield (%)

18-crown-6 (1.0) 18-crown-6 (1.0)

n.r. n.r. 16 decomp. decomp. decomp. 90

ee (%)

n.d.

96

Scheme 256. Allylic Substitution with Vinylogous Ester559

Scheme 257. Allylic Substitution with Benzyl Nitrile560

4.7.11. Water. The metal-catalyzed reactions usually need anhydrous conditions, as the water can quench reactive metal intermediate. However, in some cases, addition of water was beneficial for the reaction. For example, in the titaniumcatalyzed asymmetric aminolysis of epoxides, addition of water was found to influence the reactivity and enantioselectivity (Scheme 262). Although this reaction could work without addition of water, addition of a certain amount of water (5−15 mol %) had a positive effect on the reactivity and enantioselectivity.572 Further increasing the amount to 50 mol % led to a deterioration due to decomposition of the catalyst. Different from a previous study that addition of water to the BINOL/Ti(OiPr)4 system formed a tetrameric titanium

enhancing the Lewis acidity of metal catalyst or pre-activating the electrophile or nucleophile,566−570 but addition of TMSX in the asymmetric reaction has been reported less. An impressive finding by Franz was that TMSCl was an essential activator for scandium-catalyzed [3 + 2] annulation of allylsilanes with isatins (Scheme 261).571 No reaction was observed without adding TMSCl, while addition of TMSCl has a dramatic effect on the reaction rate without affecting the enantioselectivity. It was proposed that TMSCl might interact directly with the scandium complex by facilitating formation of the cationic catalyst or additionally enhancing the Lewis acidity of the scandium. 4105


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Scheme 258. 1,1-Arylborylation of Alkene561

Scheme 259. Cyclopropanation562

Scheme 260. Addition of Et2Zn to α-Halo Enone565

amounts of water. When the amount of water exceeds 7.8 mol %, the yield and ee dropped significantly. These results showed that the formation of the active catalyst required an equivalent of water per titanium cation. Ma et al. disclosed that the employment of 1.0 equiv of H2O as additive was significant for catalytic asymmetric allenylation of malonates (Scheme 263).577 They reasoned that addition of H2O made the two-phase reaction a three-phase reaction, by the solubility of K2CO3, and increased the efficiency of deprotonation to generate the malonate anion, thereby improving the yield.

species (BINOLate)6Ti4(μ3-OH),573−575 in this study, water might function as a proton shuttle, facilitating proton transfer between the reactants. Hintermann et al. observed that addition of a catalytic amount of water had positive effects on the yield and enantioselectivity in the titanium-catalyzed cycloisomerization of allylphenols (Table 67).576 When the reaction was conducted in dried substrate and solvent (H2O 0.1 mol %), the product was obtained in a low yield of 19%. The best results of 55% yield and 70% ee were obtained with cocatalytic

4. SUMMARY AND OUTLOOK We have highlighted a number of additives that can be used to make asymmetric reactions perfect. In most cases, the importance of an additive can be recognized by comparing the results obtained in the absence and presence of an additive. Sometimes, in order to obtain the best results, a number of additives of the same sort with different electronic and steric properties were carefully screened. As illustrated, this strategy has been demonstrated as a useful tool in the construction of chiral molecules. Without changing other reaction conditions, simply adding additives can lead to improved asymmetric catalysis, such as reduced reaction time, improved yield, increased selectivity (regio-, diastereo-, and enantioselectivity), and inverse configuration. The strategy of using additives provides another choice for optimization of an asymmetric reaction. Compared with the design or modifying the chiral catalysts for the purpose of high enantioselectivity, the benefits of using additives avoid the tedious and complicated synthesis of catalysts, as most additives are readily available and can be used directly. Addition of suitable additives sometimes can surprisingly increase the enantioselectivity from low or moderate to good or even

Scheme 261. [3 + 2] Annulation571

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Scheme 262. Aminolysis of Epoxide572

Table 67. Cycloisomerization of Allylphenol576

AUTHOR INFORMATION Corresponding Author

*E-mail: [email protected]. Notes

The authors declare no competing financial interest. Biographies entry

H2O (mol %)

yield (%)

ee (%)

1 2 3 4 5

0.1 5.1 7.8 15.4 31.3

19 55 59 32 10

60 70 60 48 7

Liang Hong was born in 1983 in Jiangsu Province, China, and received his B.Sc. degree in Biology from Lanzhou University in 2007. After he obtained his Ph.D. degree under the supervision of Professor Rui Wang in 2011 in the same university, he joined Professor Wang’s group as an assistant professor. His research interests cover asymmetric catalysis, synthetic methodology, as well as medicinal chemistry. Wangsheng Sun was born in 1987 in Gansu Province, China, and received his B.Sc. degree in Biology from Lanzhou University in 2009. He obtained his Ph.D. degree under the supervision of Professor Rui Wang in the same university in 2014. His research interests cover asymmetric catalysis, synthetic methodology, as well as medicinal chemistry.

excellent, thus greatly improving the efficiency of optimization. However, one should keep in mind that the additives are not suitable for all reactions, as in some cases they may not have positive effects or even have negative effects. As could be expected, no general theory could be extracted about which kind of additives could be used in a reaction, but we imagine that recent developments would provide ideas for the optimization of similar reactions. For new reactions, although it is hard to predict which additive may be beneficial, one could consider the automated screening process. We are confident that with the use of additives more robust and effective catalytic systems will be developed and find their application in industry.

Dongxu Yang was born in 1986 in Liaoning Province, China. After receiving his B.S. degree from Lanzhou University in 2009, he joined the research group of Professor Rui Wang to pursue his Ph.D. degree in the same university. After receiving his Ph.D. degree in 2015, he joined the research group of Professor Rui Wang as an assistant professor, working on chiral drugs design and asymmetric synthesis. Guofeng Li was born in Shanxi, China, in 1990. He received his B.S. degree in Biotechnology from Lanzhou University in 2013. He is currently a graduate student under the direction of Professor Rui

Scheme 263. Allenylation of Malonate577

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(15) Brière, J.-F.; Oudeyer, S.; Dalla, V.; Levacher, V. Recent Advances in Cooperative Ion Pairing in Asymmetric Organocatalysis. Chem. Soc. Rev. 2012, 41, 1696−1707. (16) Cozzi, P. G.; Benfatti, F.; Zoli, L. Organocatalytic Asymmetric Alkylation of Aldehydes by SN1-Type Reaction of Alcohols. Angew. Chem., Int. Ed. 2009, 48, 1313−1316. (17) Weng, Z.-T.; Li, Y.; Tian, S.-K. Catalytic Asymmetric αAlkylation of Ketones and Aldehydes with N-Benzylic Sulfonamides through Carbon-Nitrogen Bond Cleavage. J. Org. Chem. 2011, 76, 8095−8099. (18) Gao, J.; Bai, S.; Gao, Q.; Liu, Y.; Yang, Q. Acid Controlled Diastereoselectivity in Asymmetric Aldol Reaction of Cycloketones with Aldehydes Using Enamine-Based Organocatalysts. Chem. Commun. 2011, 47, 6716−6718. (19) Moteki, S. A.; Han, J.; Arimitsu, S.; Akakura, M.; Nakayama, K.; Maruoka, K. An Achiral-Acid-Induced Switch in the Enantioselectivity of a Chiral cis-Diamine-Based Organocatalyst for Asymmetric Aldol and Mannich Reactions. Angew. Chem., Int. Ed. 2012, 51, 1187−1190. (20) Brandau, S.; Maerten, E.; Jørgensen, K. A. Asymmetric Synthesis of Highly Functionalized Tetrahydrothiophenes by Organocatalytic Domino Reactions. J. Am. Chem. Soc. 2006, 128, 14986−14991. (21) Bertelsen, S.; Marigo, M.; Brandes, S.; Dinér, P.; Jørgensen, K. A. Dienamine Catalysis: Organocatalytic Asymmetric γ-Amination of α,β-Unsaturated Aldehydes. J. Am. Chem. Soc. 2006, 128, 12973− 12980. (22) Yin, X.; Zheng, Y.; Feng, X.; Jiang, K.; Wei, X.-Z.; Gao, N.; Chen, Y.-C. Asymmetric [5 + 3] Formal Cycloadditions with Cyclic Enones through Cascade Dienamine-Dienamine Catalysis. Angew. Chem., Int. Ed. 2014, 53, 6245−6248. (23) Albrecht, Ł.; Dickmeiss, G.; Weise, C. F.; Rodríguez-Escrich, C.; Jørgensen, K. A. Dienamine-Mediated Inverse-Electron-Demand Hetero-Diels−Alder Reaction by Using an Enantioselective H-BondDirecting Strategy. Angew. Chem., Int. Ed. 2012, 51, 13109−13113. (24) Albrecht, Ł.; Dickmeiss, G.; Acosta, F. C.; Rodríguez-Escrich, C.; Davis, R. L.; Jørgensen, K. A. Asymmetric Organocatalytic Formal [2 + 2]-Cycloadditions via Bifunctional H-Bond Directing Dienamine Catalysis. J. Am. Chem. Soc. 2012, 134, 2543−2546. (25) Bencivenni, G.; Galzerano, P.; Mazzanti, A.; Bartoli, G.; Melchiorre, P. Direct Asymmetric Vinylogous Michael Addition of Cyclic Enones to Nitroalkenes via Dienamine Catalysis. Proc. Natl. Acad. Sci. U. S. A. 2010, 107, 20642−20647. (26) Jiang, K.; Chen, Y.-C. The Development of Asymmetric Trienamine Catalysis. Prog. Chem. 2015, 27, 137−145. (27) Jiang, H.; Albrecht, Ł.; Jørgensen, K. A. Aminocatalytic Remote Functionalization Strategies. Chem. Sci. 2013, 4, 2287−2300. (28) Jia, Z.-J.; Jiang, H.; Li, J.-L.; Gschwend, B.; Li, Q.-Z.; Yin, X.; Grouleff, J.; Chen, Y.-C.; Jørgensen, K. A. Trienamines in Asymmetric Organocatalysis: Diels−Alder and Tandem Reactions. J. Am. Chem. Soc. 2011, 133, 5053−5061. (29) Jiang, H.; Cruz, D. C.; Li, Y.; Lauridsen, V. H.; Jørgensen, K. A. Asymmetric Organocatalytic Thio-Diels−Alder Reactions via Trienamine Catalysis. J. Am. Chem. Soc. 2013, 135, 5200−5207. (30) Albrecht, Ł.; CruzAcosta, F.; Fraile, A.; Albrecht, A.; Christensen, J.; Jørgensen, K. A. Enantioselective H-Bond-Directing Approach for Trienamine-Mediated Reactions in Asymmetric Synthesis. Angew. Chem., Int. Ed. 2012, 51, 9088−9092. (31) Halskov, K. S.; Johansen, T. K.; Davis, R. L.; Steurer, M.; Jensen, F.; Jørgensen, K. A. Cross-Trienamines in Asymmetric Organocatalysis. J. Am. Chem. Soc. 2012, 134, 12943−12496. (32) Ma, C.; Jia, Z.-J.; Liu, J.-X.; Zhou, Q.-Q.; Dong, L.; Chen, Y.-C. A Concise Assembly of Electron-Deficient 2,4-Dienes and 2,4-Dienals: Regio- and Stereoselective exo-Diels−Alder and Redox Reactions through Sequential Amine and Carbene Catalysis. Angew. Chem., Int. Ed. 2013, 52, 948−951. (33) Jia, Z.-J.; Zhou, Q.; Zhou, Q.-Q.; Chen, P.-Q.; Chen, Y.-C. ExoSelective Asymmetric Diels−Alder Reaction of 2,4-Dienals and Nitroalkenes by Trienamine Catalysis. Angew. Chem., Int. Ed. 2011, 50, 8638−8641.

Wang at the Lanzhou University as a Ph.D. student. His studies focus on organic asymmetric catalysis. Rui Wang (1963) received his Ph.D. degree in Organic Chemistry and Medicinal Chemistry in 1988 from the Sino−Japan joint Ph.D. program of Lanzhou University and Kyoto University, Japan. He then worked as a postdoctoral fellow in Lanzhou University and the University of Kansas from 1989 to 1993. He was appointed as a professor at Lanzhou University in 1994, and his interests mainly focus on asymmetric catalysis and peptide chemistry, biology, and pharmaceutical sciences. He has received a number of distinctions including the Cheung Kong Professorship in 2004, the Outstanding Young Scientist Award of the National Natural Science Foundation of China in 2005, the Thomson Reuters Research Fronts Award in 2008, the State Natural Science Award (2nd class) in 2009, the Science and Technology Award (1st class) of the Chinese Pharmaceutical Association in 2013, and the Natural Science Award (1st class) of the Ministry of Education of China in 2013.

ACKNOWLEDGMENTS This work was supported by the NSFC (21432003, 91413107, 21572278, and 21502079), the Program for Chang-Jiang Scholars and Innovative Research Team in University (IRT1137), and the Innovation Group of Gansu Province (1210RJIA002). REFERENCES (1) Vogl, E. M.; Gröger, H.; Shibasaki, M. Towards Perfect Asymmetric Catalysis: Additives and Cocatalysts. Angew. Chem., Int. Ed. 1999, 38, 1570−1577. (2) Escorihuela, J.; Burguete, M. I.; Luis, S. V. New Advances in Dual Stereocontrol for Asymmetric Reactions. Chem. Soc. Rev. 2013, 42, 5595−5617. (3) Raj, M.; Singh, V. K. Organocatalytic Reactions in Water. Chem. Commun. 2009, 6687−6703. (4) Brogan, A. P.; Dickerson, T. J.; Janda, K. D. Enamine-Based Aldol Organocatalysis in Water: Are They Really ″All Wet″? Angew. Chem., Int. Ed. 2006, 45, 8100−8102. (5) Blackmond, D. G.; Armstrong, A.; Coombe, V.; Wells, A. Water in Organocatalytic Processes: Debunking the Myths. Angew. Chem., Int. Ed. 2007, 46, 3798−3800. (6) Hayashi, Y. In Water or in the Presence of water? Angew. Chem., Int. Ed. 2006, 45, 8103−8104. (7) Erkkilä, A.; Majander, I.; Pihko, P. M. Iminium Catalysis. Chem. Rev. 2007, 107, 5416−5470. (8) Mukherjee, S.; Yang, J. W.; Hoffmann, S.; List, B. Asymmetric Enamine Catalysis. Chem. Rev. 2007, 107, 5471−5569. (9) Mahlau, M.; List, B. Asymmetric Counteranion-Directed Catalysis: Concept, Definition, and Applications. Angew. Chem., Int. Ed. 2013, 52, 518−533. (10) Ahrendt, K. A.; Borths, C. J.; MacMillan, D. W. C. New Strategies for Organic Catalysis: The First Highly Enantioselective Organocatalytic Diels−Alder Reaction. J. Am. Chem. Soc. 2000, 122, 4243−4244. (11) Jen, W. S.; Wiener, J. J. M.; MacMillan, D. W. C. New Strategies for Organic Catalysis: The First Enantioselective Organocatalytic 1,3Dipolar Cycloaddition. J. Am. Chem. Soc. 2000, 122, 9874−9875. (12) Paras, N. A.; MacMillan, D. W. C. New Strategies in Organic Catalysis: The First Enantioselective Organocatalytic Friedel−Crafts Alkylation. J. Am. Chem. Soc. 2001, 123, 4370−4371. (13) Sparr, C.; Gilmour, R. Fluoro-Organocatalysts: Conformer Equivalents as a Tool for Mechanistic Studies. Angew. Chem., Int. Ed. 2010, 49, 6520−6523. (14) Sparr, C.; Gilmour, R. Cyclopropyl Iminium Activation: Reactivity Umpolung in Enantioselective Organocatalytic Reaction Design. Angew. Chem., Int. Ed. 2011, 50, 8391−8395. 4108


Chemical Reviews

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(52) Cardinal-David, B.; Raup, D. E. A.; Scheidt, K. A. Cooperative N-Heterocyclic Carbene/Lewis Acid Catalysis for Highly Stereoselective Annulation Reactions with Homoenolates. J. Am. Chem. Soc. 2010, 132, 5345−5347. (53) Fu, Z.; Sun, H.; Chen, S.; Tiwari, B.; Li, G.; Chi, Y. R. Controlled β-Protonation and [4 + 2] Cycloaddition of Enals and Chalcones via N-Heterocyclic Carbene/Acid Catalysis: Toward Substrate Independent Reaction Control. Chem. Commun. 2013, 49, 261−263. (54) Tian, X.; Liu, Y.; Melchiorre, P. Aminocatalytic Enantioselective 1,6-Additions of Alkyl Thiols to Cyclic Dienones: Vinylogous Iminium Ion Activation. Angew. Chem., Int. Ed. 2012, 51, 6439−6442. (55) Zhang, E.; Fan, C.-A.; Tu, Y.-Q.; Zhang, F.-M.; Song, Y.-L. Organocatalytic Asymmetric Vinylogous α-Ketol Rearrangement: Enantioselective Construction of Chiral All-Carbon Quaternary Stereocenters in Spirocyclic Diketones via Semipinacol-Type 1,2Carbon Migration. J. Am. Chem. Soc. 2009, 131, 14626−14627. (56) Chen, Z.-M.; Zhang, Q.-W.; Chen, Z.-H.; Li, H.; Tu, Y.-Q.; Zhang, F.-M.; Tian, J.-M. Organocatalytic Asymmetric Halogenation/ Semipinacol Rearrangement: Highly Efficient Synthesis of Chiral αOxa-Quaternary β-Haloketones. J. Am. Chem. Soc. 2011, 133, 8818− 8821. (57) Koley, D.; Krishna, Y.; Srinivas, K.; Khan, A. A.; Kant, R. Organocatalytic Asymmetric Mannich Cyclization of Hydroxylactams with Acetals: Total Syntheses of (−)-Epilupinine, (−)-Tashiromine, and (−)-Trachelanthamidine. Angew. Chem., Int. Ed. 2014, 53, 13196− 13200. (58) Wang, S.; Li, X.; Liu, H.; Xu, L.; Zhuang, J.; Li, J.; Li, H.; Wang, W. Organocatalytic Enantioselective Direct Additions of Aldehydes to 4-Vinylpyridines and Electron-Deficient Vinylarenes and Their Synthetic Applications. J. Am. Chem. Soc. 2015, 137, 2303−2310. (59) Ke, Z.; Tan, C. K.; Chen, F.; Yeung, Y.-Y. Catalytic Asymmetric Bromoetherification and Desymmetrization of Olefinic 1,3-Diols with C-2-Symmetric Sulfides. J. Am. Chem. Soc. 2014, 136, 5627−5630. (60) Denmark, S. E.; Kalyani, D.; Collins, W. R. Preparative and Mechanistic Studies toward the Rational Development of Catalytic, Enantioselective Selenoetherification Reactions. J. Am. Chem. Soc. 2010, 132, 15752−15765. (61) Denmark, S. E.; Kornfilt, D. J. P.; Vogler, T. Catalytic Asymmetric Thiofunctionalization of Unactivated Alkenes. J. Am. Chem. Soc. 2011, 133, 15308−15311. (62) Denmark, S. E.; Jaunet, A. Catalytic, Enantioselective, Intramolecular Carbosulfenylation of Olefins. Preparative and Stereochemical Aspects. J. Org. Chem. 2014, 79, 140−171. (63) Denmark, S. E.; Jaunet, A. Catalytic, Enantioselective, Intramolecular Carbosulfenylation of Olefins. J. Am. Chem. Soc. 2013, 135, 6419−6422. (64) Lu, Y.; Zou, G.; Zhao, G. Asymmetric Intramolecular OxaMichael Reactions to Tetrahydrofurans/2H-Pyrans Catalyzed by Primary-Secondary Diamines. ACS Catal. 2013, 3, 1356−1359. (65) Lifchits, O.; Reisinger, C. M.; List, B. Catalytic Asymmetric Epoxidation of α-Branched Enals. J. Am. Chem. Soc. 2010, 132, 10227−10229. (66) Wang, X.; Reisinger, C. M.; List, B. Catalytic Asymmetric Epoxidation of Cyclic Enones. J. Am. Chem. Soc. 2008, 130, 6070− 6071. (67) Bergonzini, G.; Vera, S.; Melchiorre, P. Cooperative Organocatalysis for the Asymmetric γ-Alkylation of α-Branched Enals. Angew. Chem., Int. Ed. 2010, 49, 9685−9688. (68) Tian, X.; Cassani, C.; Liu, Y.; Moran, A.; Urakawa, A.; Galzerano, P.; Arceo, E.; Melchiorre, P. Diastereodivergent Asymmetric Sulfa-Michael Additions of α-Branched Enones using a Single Chiral Organic Catalyst. J. Am. Chem. Soc. 2011, 133, 17934−17941. (69) Dell’Amico, L.; Albrecht, Ł.; Naicker, T.; Poulsen, P. H.; Jørgensen, K. A. Beyond Classical Reactivity Patterns: Shifting from 1,4- to 1,6-Additions in Regio- and Enantioselective Organocatalyzed Vinylogous Reactions of Olefinic Lactones with Enals and 2,4-Dienals. J. Am. Chem. Soc. 2013, 135, 8063−8070.

(34) Xiao, Y.-C.; Yue, C.-Z.; Chen, P.-Q.; Chen, Y.-C. Asymmetric Dearomatic Diels−Alder Reactions of Diverse Heteroarenes via πSystem Activation. Org. Lett. 2014, 16, 3208−3211. (35) Xiong, X.-F.; Zhou, Q.; Gu, J.; Dong, L.; Liu, T.-Y.; Chen, Y.-C. Trienamine Catalysis with 2,4-Dienones: Development and Application in Asymmetric Diels−Alder Reactions. Angew. Chem., Int. Ed. 2012, 51, 4401−4404. (36) Zhang, S.-J.; Zhang, J.; Zhou, Q.-Q.; Dong, L.; Chen, Y.-C. Aminocatalytic Asymmetric Exo-Diels−Alder Reaction with Methiodide Salts of Mannich Bases and 2,4-Dienals to Construct Chiral Spirocycles. Org. Lett. 2013, 15, 968−971. (37) Ma, C.; Gu, J.; Teng, B.; Zhou, Q.-Q.; Li, R.; Chen, Y.-C. 1Azadienes as Regio- and Chemoselective Dienophiles in Aminocatalytic Asymmetric Diels−Alder Reaction. Org. Lett. 2013, 15, 6206− 6209. (38) Feng, X.; Zhou, Z.; Ma, C.; Yin, X.; Li, R.; Dong, L.; Chen, Y.-C. Trienamines Derived from Interrupted Cyclic 2,5-Dienones: Remote δ,ε-CC Bond Activation for Asymmetric Inverse-Electron-Demand Aza-Diels−Alder Reaction. Angew. Chem., Int. Ed. 2013, 52, 14173− 14176. (39) Lalonde, M. P.; McGowan, M. A.; Rajapaksa, N. S.; Jacobsen, E. N. Enantioselective Formal Aza-Diels−Alder Reactions of Enones with Cyclic Imines Catalyzed by Primary Aminothioureas. J. Am. Chem. Soc. 2013, 135, 1891−1894. (40) Zhang, H.; Lin, S.; Jacobsen, E. N. Enantioselective Selenocyclization via Dynamic Kinetic Resolution of Seleniranium Ions by Hydrogen-Bond Donor Catalysts. J. Am. Chem. Soc. 2014, 136, 16485−16488. (41) Xu, H.; Zuend, S. J.; Woll, M. G.; Tao, Y.; Jacobsen, E. N. Asymmetric Cooperative Catalysis of Strong Brønsted Acid-Promoted Reactions Using Chiral Ureas. Science 2010, 327, 986−990. (42) Lin, S.; Jacobsen, E. N. Thiourea-catalysed Ring Opening of Episulfonium Ions with Indole Derivatives by Means of Stabilizing Non-covalent Interactions. Nat. Chem. 2012, 4, 817−824. (43) Saidalimu, I.; Fang, X.; He, X.-P.; Liang, J.; Yang, X.; Wu, F. Highly Enantioselective Construction of 3-Hydroxy Oxindoles through a Decarboxylative Aldol Addition of Trifluoromethyl αFluorinated gem-Diols to N-Benzyl Isatins. Angew. Chem., Int. Ed. 2013, 52, 5566−5570. (44) Li, G.; Antilla, J. C. Highly Enantioselective Hydrogenation of Enamides Catalyzed by Chiral Phosphoric Acids. Org. Lett. 2009, 11, 1075−1078. (45) Rueping, M.; Azap, C. Cooperative Coexistence: Effective Interplay of Two Brønsted Acids in the Asymmetric Synthesis of Isoquinuclidines. Angew. Chem., Int. Ed. 2006, 45, 7832−7835. (46) Lackner, A. D.; Samant, A. V.; Toste, F. D. Single-Operation Deracemization of 3H-Indolines and Tetrahydroquinolines Enabled by Phase Separation. J. Am. Chem. Soc. 2013, 135, 14090−14093. (47) Li, J.-L.; Sahoo, B.; Daniliuc, C.-G.; Glorius, F. Conjugate Umpolung of β,β-Disubstituted Enals by Dual Catalysis with an NHeterocyclic Carbene and a Brønsted Acid: Facile Construction of Contiguous Quaternary Stereocenters. Angew. Chem., Int. Ed. 2014, 53, 10515−10519. (48) Kuwano, S.; Harada, S.; Kang, B.; Oriez, R.; Yamaoka, Y.; Takasu, K.; Yamada, K.-I. Enhanced Rate and Selectivity by Carboxylate Salt as a Basic Cocatalyst in Chiral N-Heterocyclic Carbene-Catalyzed Asymmetric Acylation of Secondary Alcohols. J. Am. Chem. Soc. 2013, 135, 11485−11488. (49) McCusker, E. O.; Scheidt, K. A. Enantioselective N-Heterocyclic Carbene Catalyzed Annulation Reactions with Imidazolidinones. Angew. Chem., Int. Ed. 2013, 52, 13616−13620. (50) Nair, V.; Vellalath, S.; Poonoth, M.; Suresh, E. N-Heterocyclic Carbene-Catalyzed Reaction of Chalcones and Enals via Homoenolate: An Efficient Synthesis of 1,3,4-Trisubstituted Cyclopentenes. J. Am. Chem. Soc. 2006, 128, 8736−8737. (51) Chiang, P.-C.; Kaeobamrung, J.; Bode, J. W. Enantioselective, Cyclopentene-Forming Annulations via NHC-Catalyzed Benzoin-OxyCope Reactions. J. Am. Chem. Soc. 2007, 129, 3520−3521. 4109


Chemical Reviews

Review

Transfer, and Derivatizations. Angew. Chem., Int. Ed. 2012, 51, 3653− 3657. (88) Stark, D. G.; Morrill, L. C.; Yeh, P.-P.; Slawin, A. M. Z.; O’Riordan, T. J. C.; Smith, A. D. Isothiourea-Mediated One-Pot Synthesis of Functionalized Pyridines. Angew. Chem., Int. Ed. 2013, 52, 11642−11646. (89) Yeh, P.-P.; Daniels, D. S. B.; Cordes, D. B.; Slawin, A. M. Z.; Smith, A. D. Isothiourea-Mediated One-Pot Synthesis of Trifluoromethyl Substituted 2-Pyrones. Org. Lett. 2014, 16, 964−967. (90) Tiseni, P. S.; Peters, R. Catalytic Asymmetric Formation of δLactones by [4 + 2] Cycloaddition of Zwitterionic Dienolates Generated from α,β-Unsaturated Acid Chlorides. Angew. Chem., Int. Ed. 2007, 46, 5325−5328. (91) Tiseni, P. S.; Peters, R. Catalytic Asymmetric Formation of δLactones from Unsaturated Acyl Halides. Chem. - Eur. J. 2010, 16, 2503−2517. (92) Shen, L.-T.; Sun, L.-H.; Ye, S. Highly Enantioselective γAmination of α,β-Unsaturated Acyl Chlorides with Azodicarboxylates: Efficient Synthesis of Chiral γ-Amino Acid Derivatives. J. Am. Chem. Soc. 2011, 133, 15894−15897. (93) Shen, L.-T.; Jia, W.-Q.; Ye, S. Catalytic [4 + 2] Cyclization of α,β-Unsaturated Acyl Chlorides with 3-Alkylenyloxindoles: Highly Diastereo- and Enantioselective Synthesis of Spirocarbocyclic Oxindoles. Angew. Chem., Int. Ed. 2013, 52, 585−588. (94) Taylor, M. S.; Jacobsen, E. N. Highly Enantioselective Catalytic Acyl-Pictet-Spengler Reactions. J. Am. Chem. Soc. 2004, 126, 10558− 10559. (95) Itoh, J.; Fuchibe, K.; Akiyama, T. Chiral Brønsted Acid Catalyzed Enantioselective Aza-Diels−Alder Reaction of Brassard’s Diene with Imines. Angew. Chem., Int. Ed. 2006, 45, 4796−4798. (96) Hatano, M.; Maki, T.; Moriyama, K.; Arinobe, M.; Ishihara, K. Pyridinium 1,1′-Binaphthyl-2,2′-disulfonates as Highly Effective Chiral Brønsted Acid-Base Combined Salt Catalysts for Enantioselective Mannich-Type Reaction. J. Am. Chem. Soc. 2008, 130, 16858−16860. (97) Uraguchi, D.; Kinoshita, N.; Ooi, T. Catalytic Asymmetric Protonation of α-Amino Acid-Derived Ketene Disilyl Acetals Using PSpiro Diaminodioxaphosphonium Barfates as Chiral Proton. J. Am. Chem. Soc. 2010, 132, 12240−12242. (98) Kawabata, T.; Nagato, M.; Takasu, K.; Fuji, K. Nonenzymatic Kinetic Resolution of Racemic Alcohols through an ’’Induced Fit’’ Process. J. Am. Chem. Soc. 1997, 119, 3169−3170. (99) Zhang, Z.; Jain, P.; Antilla, J. C. Asymmetric Reduction of Ketones by Phosphoric Acid Derived Catalysts. Angew. Chem., Int. Ed. 2011, 50, 10961−10964. (100) De, C. K.; Klauber, E. G.; Seidel, D. Merging Nucleophilic and Hydrogen Bonding Catalysis: An Anion Binding Approach to the Kinetic Resolution of Amines. J. Am. Chem. Soc. 2009, 131, 17060− 17061. (101) Klauber, E. G.; Mittal, N.; Shah, T. K.; Seidel, D. A DualCatalysis/Anion-Binding Approach to the Kinetic Resolution of Allylic Amines. Org. Lett. 2011, 13, 2464−2467. (102) Mittal, N.; Sun, D. X.; Seidel, D. Kinetic Resolution of Amines via Dual Catalysis: Remarkable Dependence of Selectivity on the Achiral Cocatalyst. Org. Lett. 2012, 14, 3084−3087. (103) Mittal, N.; Lippert, K. M.; De, C. K.; Klauber, E. G.; Emge, T. J.; Schreiner, P. R.; Seidel, D. A Dual-Catalysis Anion-Binding Approach to the Kinetic Resolution of Amines: Insights into the Mechanism via a Combined Experimental and Computational Study. J. Am. Chem. Soc. 2015, 137, 5748−5758. (104) De, C. K.; Seidel, D. Catalytic Enantioselective Desymmetrization of Meso-Diamines: A Dual Small-Molecule Catalysis Approach. J. Am. Chem. Soc. 2011, 133, 14538−14541. (105) Birrell, J. A.; Desrosiers, J.-N.; Jacobsen, E. N. Enantioselective Acylation of Silyl Ketene Acetals through Fluoride Anion-Binding Catalysis. J. Am. Chem. Soc. 2011, 133, 13872−13875. (106) De, C. K.; Mittal, N.; Seidel, D. A Dual-Catalysis Approach to the Asymmetric Steglich Rearrangement and Catalytic Enantioselective Addition of O-Acylated Azlactones to Isoquinolines. J. Am. Chem. Soc. 2011, 133, 16802−16805.

(70) Brindani, N.; Rassu, G.; Dell’Amico, L.; Zambrano, V.; Pinna, L.; Curti, C.; Sartori, A.; Battistini, L.; Casiraghi, G.; Pelosi, G.; Greco, D.; Zanardi, F. Organocatalytic, Asymmetric Eliminative [4 + 2] Cycloaddition of Allylidene Malononitriles with Enals: Rapid Entry to Cyclohexadiene-Embedding Linear and Angular Polycycles. Angew. Chem., Int. Ed. 2015, 54, 7386−7390. (71) Raja, A.; Hong, B.-C.; Lee, G.-H. Organocatalytic Enantioselective Michael-Michael-Michael-Aldol Condensation Reactions: Control of Five Stereocenters in a Quadruple-Cascade Asymmetric Synthesis of Highly Functionalized Hexahydrophenanthrenes. Org. Lett. 2014, 16, 5756−5759. (72) Yoon, T. P.; Jacobsen, E. N. Highly Enantioselective ThioureaCatalyzed Nitro-Mannich Reactions. Angew. Chem., Int. Ed. 2005, 44, 466−468. (73) Fang, Y.-Q.; Jacobsen, E. N. Cooperative, Highly Enantioselective Phosphinothiourea Catalysis of Imine-Allene [3 + 2] Cycloadditions. J. Am. Chem. Soc. 2008, 130, 5660−5661. (74) Vedejs, E.; Chen, X. Kinetic Resolution of Secondary Alcohols. Enantioselective Acylation Mediated by a Chiral (Dimethylamino)pyridine Derivative. J. Am. Chem. Soc. 1996, 118, 1809−1810. (75) Frisch, K.; Landa, A.; Saaby, S.; Jørgensen, K. A. Organocatalytic Diastereo- and Enantioselective Annulation Reactions - Construction of Optically Active 1,2-Dihydroisoquinoline and 1,2-Dihydrophthalazine Derivatives. Angew. Chem., Int. Ed. 2005, 44, 6058−6063. (76) Wu, C.; Li, G.; Sun, W.; Zhang, M.; Hong, L.; Wang, R. Organocatalytic Highly Enantioselective Monofluoroalkylation of 3Bromooxindoles: Construction of Fluorinated 3,3 ′-Disubstituted Oxindoles and Their Derivatives. Org. Lett. 2014, 16, 1960−1963. (77) Zhang, H.; Kang, H.; Hong, L.; Dong, W.; Li, G.; Zheng, X.; Wang, R. Construction of the N1-C3 Linkage Stereogenic Centers by Catalytic Asymmetric Amination Reaction of 3-Bromooxindoles with Indolines. Org. Lett. 2014, 16, 2394−2397. (78) Zhang, H.; Hong, L.; Kang, H.; Wang, R. Construction of Vicinal All-Carbon Quaternary Stereocenters by Catalytic Asymmetric Alkylation Reaction of 3-Bromooxindoles with 3-Substituted Indoles: Total Synthesis of (+)-Perophoramidine. J. Am. Chem. Soc. 2013, 135, 14098−14101. (79) Cortez, G. S.; Tennyson, R. L.; Romo, D. Intramolecular, Nucleophile-Catalyzed Aldol-Lactonization (NCAL) Reactions: Catalytic, Asymmetric Synthesis of Bicyclic β-lactones. J. Am. Chem. Soc. 2001, 123, 7945−7946. (80) Purohit, V. C.; Matla, A. S.; Romo, D. Concise Synthesis of Spirocyclic, Bridged γ-Butyrolactones via Stereospecific, Dyotropic Rearrangements of β-lactones Involving 1,2-Acyl and δ-Lactone Migrations. J. Am. Chem. Soc. 2008, 130, 10478−10479. (81) Leverett, C. A.; Purohit, V. C.; Romo, D. Enantioselective, Organocatalyzed, Intramolecular Aldol Lactonizations with Keto Acids Leading to Bi- and Tricyclic β-Lactones and Topology-Morphing Transformations. Angew. Chem., Int. Ed. 2010, 49, 9479−9483. (82) Leverett, C. A.; Purohit, V. C.; Johnson, A. G.; Davis, R. L.; Tantillo, D. J.; Romo, D. Dyotropic Rearrangements of Fused Tricyclic β-Lactones: Application to the Synthesis of (−)-Curcumanolide A and (−)-Curcumalactone. J. Am. Chem. Soc. 2012, 134, 13348−13356. (83) Belmessieri, D.; Morrill, L. C.; Simal, C.; Slawin, A. M. Z.; Smith, A. D. Organocatalytic Functionalization of Carboxylic Acids: Isothiourea-Catalyzed Asymmetric Intra- and Intermolecular Michael Addition-Lactonizations. J. Am. Chem. Soc. 2011, 133, 2714−2720. (84) Morrill, L. C.; Douglas, J.; Lebl, T.; Slawin, A. M. Z.; Fox, D. J.; Smith, A. D. Isothiourea-Mediated Asymmetric Michael-Lactonisation of Trifluoromethylenones: A Synthetic and Mechanistic Study. Chem. Sci. 2013, 4, 4146−4155. (85) Joannesse, C.; Johnston, C. P.; Concellón, C.; Simal, C.; Philp, D.; Smith, A. D. Isothiourea-Catalyzed Enantioselective Carboxy Group Transfer. Angew. Chem., Int. Ed. 2009, 48, 8914−8918. (86) Morrill, L. C.; Lebl, T.; Slawin, A. M. Z.; Smith, A. D. Catalytic Asymmetric α-Amination of Carboxylic Acids Using Isothioureas. Chem. Sci. 2012, 3, 2088−2093. (87) Simal, C.; Lebl, T.; Slawin, A. M. Z.; Smith, A. D. Dihydropyridones: Catalytic Asymmetric Synthesis, N- to C-Sulfonyl 4110


Chemical Reviews

Review

to α-Trifluoromethyl-substituted Quaternary Carbons. Org. Lett. 2007, 9, 5079−5082. (127) Taggi, A. E.; Hafez, A. M.; Wack, H.; Young, B.; Drury, W. J., III; Lectka, T. Catalytic, Asymmetric Synthesis of β-Lactams. J. Am. Chem. Soc. 2000, 122, 7831−7832. (128) Taggi, A. E.; Hafez, A. M.; Wack, H.; Young, B.; Ferraris, D.; Lectka, T. The Development of the First Catalyzed Reaction of Ketenes and Imines: Catalytic, Asymmetric Synthesis of β-Lactams. J. Am. Chem. Soc. 2002, 124, 6626−6635. (129) France, S.; Wack, H.; Hafez, A. M.; Taggi, A. E.; Witsil, D. R.; Lectka, T. Bifunctional Asymmetric Catalysis: A Tandem Nucleophile/Lewis Acid Promoted Synthesis of β-lactams. Org. Lett. 2002, 4, 1603−1605. (130) Hafez, A. M.; Dudding, T.; Wagerle, T. R.; Shah, M. H.; Taggi, A. E.; Lectka, T. A Multistage, One-Pot Procedure Mediated by A Single Catalyst: A New Approach to the Catalytic Asymmetric Synthesis of β-Amino Acids. J. Org. Chem. 2003, 68, 5819−5825. (131) Nielsen, M.; Jacobsen, C. B.; Jørgensen, K. A. Asymmetric Organocatalytic Electrophilic Phosphination. Angew. Chem., Int. Ed. 2011, 50, 3211−3214. (132) Clarke, M. L.; Fuentes, J. A. Self-assembly of Organocatalysts: Fine-tuning Organocatalytic Reactions. Angew. Chem., Int. Ed. 2007, 46, 930−933. (133) Phillips, E. M.; Riedrich, M.; Scheidt, K. A. N-Heterocyclic Carbene-Catalyzed Conjugate Additions of Alcohols. J. Am. Chem. Soc. 2010, 132, 13179−13181. (134) Dugal-Tessier, J.; O’Bryan, E. A.; Schroeder, T. B. H.; Cohen, D. T.; Scheidt, K. A. An N-Heterocyclic Carbene/Lewis Acid Strategy for the Stereoselective Synthesis of Spirooxindole Lactones. Angew. Chem., Int. Ed. 2012, 51, 4963−4967. (135) Wang, G.; Chen, X.; Miao, G.; Yao, W.; Ma, C. Divergent NHC-Catalyzed Oxidative Transformations of 3-Bromoenal: Selective Synthesis of 2H-Pyran-2-ones and Chiral Dihydropyranones. J. Org. Chem. 2013, 78, 6223−6232. (136) White, N. A.; Rovis, T. Oxidatively Initiated NHC-Catalyzed Enantioselective Synthesis of 3,4-Disubstituted Cyclopentanones from Enals. J. Am. Chem. Soc. 2015, 137, 10112−10115. (137) Ibrahem, I.; Zhao, G.-L.; Córdova, A. Direct Catalytic Enantioselective α-Aminomethylation of Aldehydes. Chem. - Eur. J. 2007, 13, 683−688. (138) Shih, J.-L.; Nguyen, T. S.; May, J. A. Organocatalyzed Asymmetric Conjugate Addition of Heteroaryl and Aryl Trifluoroborates: A Synthetic Strategy for Discoipyrrole D. Angew. Chem., Int. Ed. 2015, 54, 9931−9935. (139) Wang, Y.; Li, P.; Liang, X.; Zhang, T. Y.; Ye, J. An Efficient Enantioselective Method for Asymmetiric Michael Addition of Nitroalkanes to α,β-Unsaturated Aldehydes. Chem. Commun. 2008, 1232−1234. (140) Alza, E.; Sayalero, S.; Kasaplar, P.; Almas, D.; Pericàs, M. A. Polystyrene-Supported Diarylprolinol Ethers as Highly Efficient Organocatalysts for Michael-Type Reactions. Chem. - Eur. J. 2011, 17, 11585−11595. (141) Wang, Y.; Li, P.; Liang, X.; Ye, J. Base-base Bifunctional Catalysis: A Practical Strategy for Asymmetric Michael Addition of Malonates to α,β-Unsaturated Aldehydes. Adv. Synth. Catal. 2008, 350, 1383−1389. (142) Hayashi, M.; Nakamura, S. Catalytic Enantioselective Protonation of α-Oxygenated Ester Enolates Prepared through Phospha-Brook Rearrangement. Angew. Chem., Int. Ed. 2011, 50, 2249−2252. (143) Nakamura, S.; Hayashi, M.; Hiramatsu, Y.; Shibata, N.; Funahashi, Y.; Toru, T. Catalytic Enantioselective Hydrophosphonylation of Ketimines Using Cinchona Alkaloids. J. Am. Chem. Soc. 2009, 131, 18240−18241. (144) Hong, L.; Sun, W.; Liu, C.; Zhao, D.; Wang, R. Enantioselective Construction of Allylic Phosphine Oxides through Substitution of Morita−Baylis−Hillman Carbonates with Phosphine Oxides. Chem. Commun. 2010, 46, 2856−2858.

(107) Peris, G.; Jakobsche, C. E.; Miller, S. J. Aspartate-Catalyzed Asymmetric Epoxidation Reactions. J. Am. Chem. Soc. 2007, 129, 8710−8711. (108) Kolundzic, F.; Noshi, M. N.; Tjandra, M.; Movassaghi, M.; Miller, S. J. Chemoselective and Enantioselective Oxidation of Indoles Employing Aspartyl Peptide Catalysts. J. Am. Chem. Soc. 2011, 133, 9104−9111. (109) Imbriglio, J. E.; Vasbinder, M. M.; Miller, S. J. Dual Catalyst Control in the Amino Acid-Peptide-Catalyzed Enantioselective Baylis−Hillman Reaction. Org. Lett. 2003, 5, 3741−3743. (110) Chen, S.-H.; Hong, B.-C.; Su, C.-F.; Sarshar, S. An Unexpected Inversion of Enantioselectivity in the Proline Catalyzed Intramolecular Baylis−Hillman Reaction. Tetrahedron Lett. 2005, 46, 8899−8903. (111) Ward, D. E.; Sales, M.; Sasmal, P. K. Syn-Anti Isomerization of Aldols by Enolization. J. Org. Chem. 2004, 69, 4808−4815. (112) Mitsumori, S.; Zhang, H.; Cheong, P. H.-Y.; Houk, K. N.; Tanaka, F.; Barbas, C. F., III Direct Asymmetric Anti-Mannich-Type Reactions Catalyzed by a Designed Amino Acid. J. Am. Chem. Soc. 2006, 128, 1040−1041. (113) Utsumi, N.; Zhang, H.; Tanaka, F.; Barbas, C. F., III A Way to Highly Enantiomerically Enriched Aza-Morita−Baylis−Hillman-Type Products. Angew. Chem., Int. Ed. 2007, 46, 1878−1880. (114) Lee, A.; Younai, A.; Price, C. K.; Izquierdo, J.; Mishra, R. K.; Scheidt, K. A. Enantioselective Annulations for Dihydroquinolones by in Situ Generation of Azolium Enolates. J. Am. Chem. Soc. 2014, 136, 10589−10592. (115) Reyes, E.; Jiang, H.; Milelli, A.; Elsner, P.; Hazell, R. G.; Jøgensen, K. A. How to Make Five Contiguous Stereocenters in One Reaction: Asymmetric Organocatalytic Synthesis of Pentasubstituted Cyclohexanes. Angew. Chem., Int. Ed. 2007, 46, 9202−9205. (116) Liu, Y.-K.; Ma, C.; Jiang, K.; Liu, T.-Y.; Chen, Y.-C. Asymmetric Tandem Michael Addition-Wittig Reaction to Cyclohexenone Annulation. Org. Lett. 2009, 11, 2848−2851. (117) Blackmond, D. G.; Moran, A.; Hughes, M.; Armstrong, A. Unusual Reversal of Enantioselectivity in the Proline-Mediated αAmination of Aldehydes Induced by Tertiary Amine Additives. J. Am. Chem. Soc. 2010, 132, 7598−7599. (118) Hein, J. E.; Burés, J.; Lam, Y.-H.; Hughes, M.; Houk, K. N.; Armstrong, A.; Blackmond, D. G. Enamine Carboxylates as Stereodetermining Intermediates in Prolinate Catalysis. Org. Lett. 2011, 13, 5644−5647. (119) Martínez-Castañeda, Á .; Poladura, B.; Rodríguez-Solla, H.; Concellón, C.; del Amo, V. Direct Aldol Reactions Catalyzed by a Heterogeneous Guanidinium Salt/Proline System under Solvent-Free Conditions. Org. Lett. 2011, 13, 3032−3035. (120) Martínez-Castañeda, Á .; Poladura, B.; Rodríguez-Solla, H.; Concellón, C.; del Amo, V. Highly Enantioselective Proline-Catalysed Direct Aldol Reaction of Chloroacetone and Aromatic Aldehydes. Chem. - Eur. J. 2012, 18, 5188−5190. (121) Martínez-Castañ eda, Á .; Kędziora, K.; Lavandera, I.; Rodríguez-Solla, H.; Concellón, C.; del Amo, V. Highly Enantioselective Synthesis of α-Azido-β-Hydroxy Methyl Ketones Catalyzed by a Cooperative Proline-Guanidinium Salt System. Chem. Commun. 2014, 50, 2598−2600. (122) Martínez-Castañeda, Á .; Rodríguez-Solla, H.; Concellón, C.; del Amo, V. Switching Diastereoselectivity in Proline-Catalyzed Aldol Reactions. J. Org. Chem. 2012, 77, 10375−10381. (123) List, B.; Č orić, I.; Grygorenko, O. O.; Kaib, P. S. J.; Komarov, I.; Lee, A.; Leutzsch, M.; Pan, S. C.; Tymtsunik, A. V.; van Gemmeren, M. The Catalytic Asymmetric α-Benzylation of Aldehydes. Angew. Chem., Int. Ed. 2014, 53, 282−285. (124) Vignola, N.; List, B. Catalytic Asymmetric Intramolecular αAlkylation of Aldehydes. J. Am. Chem. Soc. 2004, 126, 450−451. (125) Schneider, E. M.; Raso, R. A.; Hofer, C. J.; Zeltner, M.; Stettler, R. D.; Hess, S. C.; Grass, R. N.; Stark, W. J. Magnetic Superbasic Proton Sponges Are Readily Removed and Permit Direct Product Isolation. J. Org. Chem. 2014, 79, 10908−10915. (126) Tur, F.; Saá, J. M. Direct, Catalytic Enantioselective Nitroaldol (Henry) Reaction of Trifluoromethyl Ketones: An Asymmetric Entry 4111


Chemical Reviews

Review

(145) Sun, W.; Hong, L.; Liu, C.; Wang, R. Base-Accelerated Enantioselective Substitution of Morita−Baylis−Hillman Carbonates with Dialkyl Phosphine Oxides. Org. Lett. 2010, 12, 3914−3917. (146) Yamaoka, Y.; Miyabe, H.; Takemoto, Y. Catalytic Enantioselective Petasis-Type Reaction of Quinolines Catalyzed by a Newly Designed Thiourea Catalyst. J. Am. Chem. Soc. 2007, 129, 6686−6687. (147) Guo, C.; Song, J.; Huang, J.-Z.; Chen, P.-H.; Luo, S.-W.; Gong, L.-Z. Core-Structure-Oriented Asymmetric Organocatalytic Substitution of 3-Hydroxyoxindoles: Application in the Enantioselective Total Synthesis of (+)-Folicanthine. Angew. Chem., Int. Ed. 2012, 51, 1046− 1050. (148) Wen, Y.; Xiong, Y.; Chang, L.; Huang, J.; Liu, X.; Feng, X. Chiral Bisformamides as Effective Organocatalysts for the Asymmetric One-Pot, Three-Component Strecker Reaction. J. Org. Chem. 2007, 72, 7715−7719. (149) Zhang, G.; Ma, Y.; Wang, S.; Zhang, Y.; Wang, R. Enantioselective Metal/Organo-Catalyzed Aerobic Oxidative sp3 C-H Olefination of Tertiary Amines Using Molecular Oxygen as the Sole Oxidant. J. Am. Chem. Soc. 2012, 134, 12334−12337. (150) Romanov-Michailidis, F.; Guénée, L.; Alexakis, A. Enantioselective Organocatalytic Fluorination-Induced Wagner-Meerwein Rearrangement. Angew. Chem., Int. Ed. 2013, 52, 9266−9270. (151) Zu, L.; Zhang, S.; Xie, H.; Wang, W. Catalytic Asymmetric Oxa-Michael-Michael Cascade for Facile Construction of Chiral Chromans via an Aminal Intermediate. Org. Lett. 2009, 11, 1627− 1630. (152) Li, H.; Zu, L.; Xie, H.; Wang, J.; Wang, W. Highly Enantio- and Diastereoselective Organocatalytic Cascade Aza-Michael-Michael Reactions: A Direct Method for the Synthesis of Trisubstituted Chiral Pyrrolidines. Chem. Commun. 2008, 5636−5638. (153) Wang, J.; Li, H.; Xie, H.; Zu, L.; Shen, X.; Wang, W. Organocatalytic Enantioselective Cascade Michael-Aldol Condensation Reactions: Efficient Assembly of Densely Functionalized Chiral Cyclopentenes. Angew. Chem., Int. Ed. 2007, 46, 9050−9053. (154) Deiana, L.; Dziedzic, P.; Zhao, G.-L.; Vesely, J.; Ibrahem, I.; Rios, R.; Sun, J.; Córdova, A. Catalytic Asymmetric Aziridination of α,β-Unsaturated Aldehydes. Chem. - Eur. J. 2011, 17, 7904−7917. (155) Deiana, L.; Zhao, G.-L.; Lin, S.; Dziedzic, P.; Zhang, Q.; Leijonmarck, H.; Córdova, A. Organocatalytic Enantioselective Aziridination of α-Substituted α,β-Unsaturated Aldehydes: Asymmetric Synthesis of Terminal Aziridines. Adv. Synth. Catal. 2010, 352, 3201−3207. (156) Molnár, I. G.; Tanzer, E.-M.; Daniliuc, C.; Gilmour, R. Enantioselective Aziridination of Cyclic Enals Facilitated by the Fluorine-Iminium Ion Gauche Effect. Chem. - Eur. J. 2014, 20, 794− 800. (157) Hayashi, Y.; Itoh, T.; Ishikawa, H. Oxidative and Enantioselective Cross-Coupling of Aldehydes and Nitromethane Catalyzed by Diphenylprolinol Silyl Ether. Angew. Chem., Int. Ed. 2011, 50, 3920−3924. (158) Hayashi, Y.; Itoh, T.; Ishikawa, H. Organocatalyst-Mediated Dehydrogenation of Aldehydes to α,β-Unsaturated Aldehydes, and Oxidative and Enantioselective Reaction of Aldehydes and Nitromethane Catalyzed by Diphenylprolinol Silyl Ether. Adv. Synth. Catal. 2013, 355, 3661−3669. (159) Rong, Z.-Q.; Jia, M.-Q.; You, S.-L. Enantioselective NHeterocyclic Carbene-Catalyzed Michael Addition to α,β-Unsaturated Aldehydes by Redox Oxidation. Org. Lett. 2011, 13, 4080−4083. (160) Liu, Y.; Liu, X.; Wang, M.; He, P.; Lin, L.; Feng, X. Enantioselective Synthesis of 3,4-Dihydropyran Derivatives via Organocatalytic Michael Reaction of α,β-Unsaturated Enones. J. Org. Chem. 2012, 77, 4136−4142. (161) Sohtome, Y.; Takemura, N.; Takada, K.; Takagi, R.; Iguchi, T.; Nagasawa, K. Organocatalytic Asymmetric Nitroaldol Reaction: Cooperative Effects of Guanidine and Thiourea Functional Groups. Chem. - Asian J. 2007, 2, 1150−1160. (162) Takada, K.; Takemura, N.; Cho, K.; Sohtome, Y.; Nagasawa, K. Asymmetric Organocatalytic Nitroaldol Reaction of α-Ketoesters:

Stereoselective Construction of Chiral Tertiary Alcohols at Subzero Temperature. Tetrahedron Lett. 2008, 49, 1623−1626. (163) Wang, M.; Wang, B. M.; Shi, L.; Tu, Y. Q.; Fan, C.-A.; Wang, S. H.; Hu, X. D.; Zhang, S. Y. Quinine/Selectfluor Combination Induced Asymmetric Semipinacol Rearrangement of Allylic Alcohols: An Effective and Enantioselective Approach to α-Quaternary β-Fluoro Aldehydes. Chem. Commun. 2005, 5580−5582. (164) Chen, Z.-M.; Yang, B.-M.; Chen, Z.-H.; Zhang, Q.-W.; Wang, M.; Tu, Y.-Q. Organocatalytic Asymmetric Fluorination/Semipinacol Rearrangement: An Efficient Approach to Chiral β-Fluoroketones. Chem. - Eur. J. 2012, 18, 12950−12954. (165) Ishimaru, T.; Shibata, N.; Horikawa, T.; Yasuda, N.; Nakamura, S.; Toru, T.; Shiro, M. Cinchona Alkaloid Catalyzed Enantioselective Fluorination of Allyl Silanes, Silyl Enol Ethers, and Oxindoles. Angew. Chem., Int. Ed. 2008, 47, 4157−4161. (166) Sun, W.; Zhu, G.; Wu, C.; Hong, L.; Wang, R. An Organocatalytic Cascade Strategy for the Enantioselective Construction of Spirocyclopentane Bioxindoles Containing Three Contiguous Stereocenters and Two Spiro Quaternary Centers. Chem. - Eur. J. 2012, 18, 6737−6741. (167) Chen, W.; Jing, Z.; Chin, K. F.; Qiao, B.; Zhao, Y.; Yan, L.; Tan, C.-H.; Jiang, Z. Catalytic Asymmetric Conjugate Addition of Mercaptans to β-Substituted-β-Trifluoromethyl Oxazolidinone Enoates: Access to Chiral Trifluoromethylated Tertiary Thioethers and Thiols. Adv. Synth. Catal. 2014, 356, 1292−1300. (168) Tian, L.; Hu, X.-Q.; Li, Y.-H.; Xu, P.-F. Organocatalytic Asymmetric Multicomponent Cascade Reaction via 1,3-Proton Shift and [3 + 2] Cycloaddition: An Efficient Strategy for the Synthesis of Oxindole Derivatives. Chem. Commun. 2013, 49, 7213−7215. (169) Liu, Q.; Perreault, S.; Rovis, T. Catalytic Asymmetric Intermolecular Stetter Reaction of Glyoxamides with Alkylidenemalonates. J. Am. Chem. Soc. 2008, 130, 14066−14067. (170) Qian, H.; Zhao, W.; Wang, Z.; Sun, J. Organocatalytic Enantioand Diastereoselective Synthesis of 1,2-Dihydronaphthalenes from Isobenzopyrylium Ions. J. Am. Chem. Soc. 2015, 137, 560−563. (171) Lin, A.; Mao, H.; Zhu, X.; Ge, H.; Tan, R.; Zhu, C.; Cheng, Y. Organocatalytic Enantioselective Amination of Morita−Baylis−Hillman Carbonates with Masked Ammonia: A Facile Method for the Synthesis of Unprotected α-Methylene-β-Amino Esters. Chem. - Eur. J. 2011, 17, 13676−13679. (172) Hatano, M.; Maki, T.; Moriyama, K.; Arinobe, M.; Ishihara, K. Pyridinium 1,1′-Binaphthyl-2,2 ′-Disulfonates as Highly Effective Chiral Brønsted Acid-Base Combined Salt Catalysts for Enantioselective Mannich-Type Reaction. J. Am. Chem. Soc. 2008, 130, 16858− 16860. (173) Caruana, L.; Fochi, M.; Franchini, M. C.; Ranieri, S.; Mazzanti, A.; Bernardi, L. Asymmetric Synthesis of 3,4-Annulated Indoles through An Organocatalytic Cascade Approach. Chem. Commun. 2014, 50, 445−447. (174) Larson, S. E.; Li, G.; Rowland, G. B.; Junge, D.; Huang, R.; Woodcock, H. L.; Antilla, J. C. Catalytic Asymmetric Aza-Darzens Reaction with a Vaulted Biphenanthrol Magnesium Phosphate Salt. Org. Lett. 2011, 13, 2188−2191. (175) Ingle, G. K.; Liang, Y.; Mormino, M. G.; Li, G.; Fronczek, F. R.; Antilla, J. C. Chiral Magnesium BINOL Phosphate-Catalyzed Phosphination of Imines: Access to Enantioenriched α-Amino Phosphine Oxides. Org. Lett. 2011, 13, 2054−2057. (176) Nimmagadda, S. K.; Zhang, Z.; Antilla, J. C. Asymmetric OnePot Synthesis of 1,3-Oxazolidines and 1,3-Oxazinanes via Hemiaminal Intermediates. Org. Lett. 2014, 16, 4098−4101. (177) Li, G.; Liang, T.; Wojtas, L.; Antilla, J. C. An Asymmetric Diels−Alder Reaction Catalyzed by Chiral Phosphate Magnesium Complexes: Highly Enantioselective Synthesis of Chiral Spirooxindoles. Angew. Chem., Int. Ed. 2013, 52, 4628−4632. (178) Raup, D. E. A.; Cardinal-David, B.; Holte, D.; Scheidt, K. A. Cooperative Catalysis by Carbenes and Lewis Acids in A Highly Stereoselective Route to γ-Lactams. Nat. Chem. 2010, 2, 766−771. 4112


Chemical Reviews

Review

Catalyzed by an Aminoalcohol-Derived, Boron-Based Catalyst. J. Am. Chem. Soc. 2014, 136, 3780−3783. (197) Fuerst, D. E.; Jacobsen, E. N. Thiourea-Catalyzed Enantioselective Cyanosilylation of Ketones. J. Am. Chem. Soc. 2005, 127, 8964− 8965. (198) Zuend, S. J.; Jacobsen, E. N. Cooperative Catalysis by Tertiary Amino-Thioureas: Mechanism and Basis for Enantioselectivity of Ketone Cyanosilylation. J. Am. Chem. Soc. 2007, 129, 15872−15883. (199) Zuend, S. J.; Jacobsen, E. N. Mechanism of Amido-Thiourea Catalyzed Enantioselective Imine Hydrocyanation: Transition State Stabilization via Multiple Non-Covalent Interactions. J. Am. Chem. Soc. 2009, 131, 15358−15374. (200) Guin, J.; Varseev, G.; List, B. Catalytic Asymmetric Protonation of Silyl Ketene Imines. J. Am. Chem. Soc. 2013, 135, 2100−2103. (201) Cheon, C. H.; Yamamoto, H. A Brønsted Acid Catalyst for the Enantioselective Protonation Reaction. J. Am. Chem. Soc. 2008, 130, 9246−9247. (202) Uraguchi, D.; Ueki, Y.; Ooi, T. Chiral Organic Ion Pair Catalysts Assembled Through a Hydrogen-Bonding Network. Science 2009, 326, 120−123. (203) Kalek, M.; Fu, G. C. Phosphine-Catalyzed Doubly Stereoconvergent γ-Additions of Racemic Heterocycles to Racemic Allenoates: The Catalytic Enantioselective Synthesis of Protected α,α-Disubstituted α-Amino Acid Derivatives. J. Am. Chem. Soc. 2015, 137, 9438−9442. (204) Smith, S. W.; Fu, G. C. Asymmetric Carbon-Carbon Bond Formation γ to a Carbonyl Group: Phosphine-Catalyzed Addition of Nitromethane to Allenes. J. Am. Chem. Soc. 2009, 131, 14231−14233. (205) Abermil, N.; Masson, G.; Zhu, J. Highly Enantioselective Aza Morita−Baylis−Hillman Reaction Catalyzed by Bifunctional βIsocupreidine Derivatives. J. Am. Chem. Soc. 2008, 130, 12596−12597. (206) Abermil, N.; Masson, G.; Zhu, J. Invertible Enantioselectivity in 6′-Deoxy-6′-Acylamino-β-Isocupreidine-Catalyzed Asymmetric AzaMorita−Baylis−Hillman Reaction: Key Role of Achiral Additive. Org. Lett. 2009, 11, 4648−4651. (207) Kawahara, S.; Nakano, A.; Esumi, T.; Iwabuchi, Y.; Hatakeyama, S. β-Isocupreidine-Catalyzed Asymmetric Baylis−Hillman Reaction of Imines. Org. Lett. 2003, 5, 3103−3105. (208) Nakano, A.; Takahashi, K.; Ishihara, J.; Hatakeyama, S. βIsocupreidine-catalyzed Baylis -Hillman Reaction of Chiral N-boc-αAmino Aldehydes. Org. Lett. 2006, 8, 5357−5360. (209) Shi, M.; Xu, Y.-M.; Shi, Y.-L. Catalytic, Asymmetric AzaBaylis−Hillman Reaction of N-Sulfonated Imines with Activated Olefins by Quinidine-Derived Chiral Amines. Chem. - Eur. J. 2005, 11, 1794−1802. (210) Yao, Y.; Li, J.-L.; Zhou, Q.-Q.; Dong, L.; Chen, Y.-C. Enantioselective Aza-Morita−Baylis−Hillman Reaction with Ketimines and Acrolein Catalyzed by Organic Assemblies. Chem. - Eur. J. 2013, 19, 9447−9451. (211) DiRocco, D. A.; Rovis, T. Catalytic Asymmetric Intermolecular Stetter Reaction of Enals with Nitroalkenes: Enhancement of Catalytic Efficiency through Bifunctional Additives. J. Am. Chem. Soc. 2011, 133, 10402−10405. (212) Filloux, C. M.; Lathrop, S. P.; Rovis, T. Multicatalytic, Asymmetric Michael/Stetter Reaction of Salicylaldehydes and Activated Alkynes. Proc. Natl. Acad. Sci. U. S. A. 2010, 107, 20666− 20671. (213) Itoh, J.; Fuchibe, K.; Akiyama, T. Chiral Phosphoric Acid Catalyzed Enantioselective Friedel−Crafts Alkylation of Indoles with Nitroalkenes: Cooperative Effect of 3Å Molecular Sieves. Angew. Chem., Int. Ed. 2008, 47, 4016−4018. (214) Sakamoto, T.; Itoh, J.; Mori, K.; Akiyama, T. Chiral Brønsted Acid Catalyzed Asymmetric Friedel−Crafts Alkylation Reaction of Indoles with α,β-Unsaturated Ketones: Short Access to Optically Active 2-and 3-Substituted Indole Derivatives. Org. Biomol. Chem. 2010, 8, 5448−5454.

(179) Lu, S.; Poh, S. B.; Siau, W.-Y.; Zhao, Y. Kinetic Resolution of Tertiary Alcohols: Highly Enantioselective Access to 3-Hydroxy-3Substituted Oxindoles. Angew. Chem., Int. Ed. 2013, 52, 1731−1734. (180) Ren, L.; Lei, T.; Ye, J.-X.; Gong, L.-Z. Step-Economical Synthesis of Tetrahydroquinolines by Asymmetric Relay Catalytic Friedlander Condensation/Transfer Hydrogenation. Angew. Chem., Int. Ed. 2012, 51, 771−774. (181) Cohen, D. T.; Scheidt, K. A. Cooperative Lewis Acid/NHeterocyclic Carbene Catalysis. Chem. Sci. 2012, 3, 53−57. (182) Domingo, L. R.; Zaragozá, R. J.; Arnó, M. Understanding the Cooperative NHC/LA Catalysis for Stereoselective Annulation Reactions with Homoenolates. A DFT Study. Org. Biomol. Chem. 2011, 9, 6616−6622. (183) Wadamoto, M.; Phillips, E. M.; Reynolds, T. E.; Scheidt, K. A. Enantioselective Synthesis of α,α-Disubstituted Cyclopentenes by an N-Heterocyclic Carbene-Catalyzed Desymmetrization of 1,3-Diketones. J. Am. Chem. Soc. 2007, 129, 10098−10099. (184) Sohn, S. S.; Rosen, E. L.; Bode, J. W. N-Heterocyclic CarbeneCatalyzed Generation of Homoenolates: γ-Butyrolactones by Direct Annulations of Enals and Aldehydes. J. Am. Chem. Soc. 2004, 126, 14370−14371. (185) Cohen, D. T.; Cardinal-David, B.; Roberts, J. M.; Sarjeant, A. A.; Scheidt, K. A. NHC-Catalyzed/Titanium(IV)-Mediated Highly Diastereo- and Enantioselective Dimerization of Enals. Org. Lett. 2011, 13, 1068−1071. (186) Cohen, D. T.; Cardinal-David, B.; Scheidt, K. A. Lewis Acid Activated Synthesis of Highly Substituted Cyclopentanes by the NHeterocyclic Carbene Catalyzed Addition of Homoenolate Equivalents to Unsaturated Ketoesters. Angew. Chem., Int. Ed. 2011, 50, 1678−1682. (187) Ma, H.; Matsuzaki, K.; Yang, Y.-D.; Tokunaga, E.; Nakane, D.; Ozawa, T.; Masuda, H.; Shibata, N. Enantioselective Monofluoromethylation of Aldehydes with 2-Fluoro-1,3-Benzodithiole-1,1,3,3Tetraoxide Catalyzed by a Bifunctional Cinchona Alkaloid-Derived Thiourea-Titanium Complex. Chem. Commun. 2013, 49, 11206− 11208. (188) Chen, W.; Yang, W.; Yan, L.; Tan, C.-H.; Jiang, Z. Bicyclic Guanidinium-Catalyzed Enantioselective Phase-Transfer Alkylation: Direct Access to Pyrroloindolines and Furoindolines. Chem. Commun. 2013, 49, 9854−9856. (189) Lv, J.; Zhang, L.; Zhou, Y.; Nie, Z.; Luo, S.; Cheng, J.-P. Asymmetric Binary Acid Catalysis: A Regioselectivity Switch between Enantioselective 1,2-and 1,4-Addition through Different Counteranions of InIII. Angew. Chem., Int. Ed. 2011, 50, 6610−6614. (190) Xin, J.; Chang, L.; Hou, Z.; Shang, D.; Liu, X.; Feng, X. An Enantioselective Biginelli Reaction Catalyzed by a Simple Chiral Secondary Amine and Achiral Brønsted Acid by a Dual-Activation Route. Chem. - Eur. J. 2008, 14, 3177−3181. (191) Saha, S.; Moorthy, J. N. Enantioselective Organocatalytic Biginelli Reaction: Dependence of the Catalyst on Sterics, Hydrogen Bonding, and Reinforced Chirality. J. Org. Chem. 2011, 76, 396−402. (192) Arseniyadis, S.; Subhash, P. V.; Valleix, A.; Mathew, S. P.; Blackmond, D. G.; Wagner, A.; Mioskowski, C. Tuning the Enantioselective N-Acetylation of Racemic Amines: A Spectacular Salt Effect. J. Am. Chem. Soc. 2005, 127, 6138−6139. (193) Ogura, Y.; Akakura, M.; Sakakura, A.; Ishihara, K. Enantioselective Cyanoethoxycarbonylation of Isatins Promoted by a Lewis Base-Brønsted Acid Cooperative Catalyst. Angew. Chem., Int. Ed. 2013, 52, 8299−8303. (194) Cheng, Y. A.; Yu, W. Z.; Yeung, Y.-Y. Carbamate-Catalyzed Enantioselective Bromolactamization. Angew. Chem., Int. Ed. 2015, 54, 12102. (195) Silverio, D. L.; Torker, S.; Pilyugina, T.; Vieira, E. M.; Snapper, M. L.; Haeffner, F.; Hoveyda, A. H. Simple Organic Molecules as Catalysts for Enantioselective Synthesis of Amines and Alcohols. Nature 2013, 494, 216−221. (196) Wu, H.; Haeffner, F.; Hoveyda, A. H. An Efficient, Practical, and Enantioselective Method for Synthesis of Homoallenylamides 4113


Chemical Reviews

Review

(232) Č orić, I.; Vellalath, S.; List, B. Catalytic Asymmetric Transacetalization. J. Am. Chem. Soc. 2010, 132, 8536−8537. (233) Č orić, I.; Müller, S.; List, B. Kinetic Resolution of Homoaldols via Catalytic Asymmetric Transacetalization. J. Am. Chem. Soc. 2010, 132, 17370−17373. (234) Terada, M.; Soga, K.; Momiyama, N. Enantioselective Activation of Aldehydes by Chiral Phosphoric Acid Catalysts in an Aza-Ene-Type Reaction between Glyoxylate and Enecarbamate. Angew. Chem., Int. Ed. 2008, 47, 4122−4125. (235) Terada, M.; Ikehara, T.; Ube, H. Enantioselective 1,4-Addition Reactions of Diphenyl Phosphite to Nitroalkenes Catalyzed by an Axially Chiral Guanidine. J. Am. Chem. Soc. 2007, 129, 14112−14113. (236) Terada, M.; Moriya, K.; Kanomata, K.; Sorimachi, K. Chiral Brønsted Acid Catalyzed Stereoselective Addition of Azlactones to 3Vinylindoles for Facile Access to Enantioenriched Tryptophan Derivatives. Angew. Chem., Int. Ed. 2011, 50, 12586−12590. (237) Gu, Q.; Rong, Z.-Q.; Zheng, C.; You, S.-L. Desymmetrization of Cyclohexadienones via Brønsted Acid-Catalyzed Enantioselective Oxo-Michael Reaction. J. Am. Chem. Soc. 2010, 132, 4056−4057. (238) Wang, S.-G.; You, S.-L. Hydrogenative Dearomatization of Pyridine and an Asymmetric Aza-Friedel−Crafts Alkylation Sequence. Angew. Chem., Int. Ed. 2014, 53, 2194−2197. (239) Yin, Q.; You, S.-L. Chiral Phosphoric Acid-catalysed Friedel− Crafts Alkylation Reaction of Indoles with Racemic Spiro Indolin-3Ones. Chem. Sci. 2011, 2, 1344−1348. (240) Cai, Q.; Zheng, C.; You, S.-L. Enantioselective Intramolecular Aza-Michael Additions of Indoles Catalyzed by Chiral Phosphoric Acids. Angew. Chem., Int. Ed. 2010, 49, 8666−8669. (241) Sheng, Y.-F.; Gu, Q.; Zhang, A.-J.; You, S.-L. Chiral Brønsted Acid-Catalyzed Asymmetric Friedel−Crafts Alkylation of Pyrroles with Nitroolefins. J. Org. Chem. 2009, 74, 6899−6901. (242) Sheng, Y.-F.; Li, G.-Q.; Kang, Q.; Zhang, A.-J.; You, S.-L. Asymmetric Friedel−Crafts Reaction of 4,7-Dihydroindoles with Nitroolefins by Chiral Brønsted Acids under Low Catalyst Loading. Chem. - Eur. J. 2009, 15, 3351−3354. (243) Hashimoto, T.; Kimura, H.; Nakatsu, H.; Maruoka, K. Synthetic Application and Structural Elucidation of Axially Chiral Dicarboxylic Acid: Asymmetric Mannich-Type Reaction with Diazoacetate, (Diazomethyl)phosphonate, and (Diazomethyl)sulfone. J. Org. Chem. 2011, 76, 6030−6037. (244) Zhang, H.; Wen, X.; Gan, L.; Peng, Y. Highly Efficient Asymmetric Mannich Reaction of Dialkyl α-Diazomethylphosphonates with N-Carbamoyl Imines Catalyzed by Chiral Brønsted Acids. Org. Lett. 2012, 14, 2126−2129. (245) Hashimoto, T.; Kimura, H.; Kawamata, Y.; Maruoka, K. A Catalytic Asymmetric Ugi-Type Reaction With Acyclic Azomethine Imines. Angew. Chem., Int. Ed. 2012, 51, 7279−7281. (246) Hashimoto, T.; Nakatsu, H.; Takiguchi, Y.; Maruoka, K. Axially Chiral Dicarboxylic Acid Catalyzed Activation of Quinone Imine Ketals: Enantioselective Arylation of Enecarbamates. J. Am. Chem. Soc. 2013, 135, 16010−16013. (247) Hashimoto, T.; Uchiyama, N.; Maruoka, K. Trans-Selective Asymmetric Aziridination of Diazoacetamides and N-Boc Imines Catalyzed by Axially Chiral Dicarboxylic Acid. J. Am. Chem. Soc. 2008, 130, 14380−14381. (248) Hashimoto, T.; Gálvez, A. O.; Maruoka, K. In Situ Assembled Boronate Ester Assisted Chiral Carboxylic Acid Catalyzed Asymmetric Trans-Aziridinations. J. Am. Chem. Soc. 2013, 135, 17667−17670. (249) Chauhan, P.; Chimni, S. S. Asymmetric Addition of Indoles to Isatins Catalysed by Bifunctional Modified Cinchona Alkaloid Catalysts. Chem. - Eur. J. 2010, 16, 7709−7713. (250) Li, G.-X.; Qu, J. Enantioselective Friedel−Crafts Reactions between Phenols and N-Tosylaldimines Catalyzed by a LeucineDerived Bifunctional Catalyst. Chem. Commun. 2012, 48, 5518−5520. (251) Tian, X.; Jiang, K.; Peng, J.; Du, W.; Chen, Y.-C. Organocatalytic Stereoselective Mannich Reaction of 3-Substituted Oxindoles. Org. Lett. 2008, 10, 3583−3586. (252) Li, X.; Xue, X.-S.; Liu, C.; Wang, B.; Tan, B.-X.; Jin, J.-L.; Zhang, Y.-Y.; Dong, N.; Cheng, J.-P. Asymmetric Michael Addition

(215) Lou, S.; Moquist, P. N.; Schaus, S. E. Asymmetric Allylboration of Acyl Imines Catalyzed by Chiral Diols. J. Am. Chem. Soc. 2007, 129, 15398−15404. (216) Takizawa, S.; Kiriyama, K.; Ieki, K.; Sasai, H. A Bifunctional Spiro-Type Organocatalyst with High Enantiocontrol: Application to the Aza-Morita−Baylis−Hillman. Chem. Commun. 2011, 47, 9227− 9229. (217) Li, N.; Song, J.; Tu, X.-F.; Liu, B.; Chen, X.-H.; Gong, L.-Z. Organocatalytic Asymmetric Intramolecular [3 + 2] Cycloaddition: A Straightforward Approach to Access Multiply Substituted Hexahydrochromeno[4,3-b]pyrrolidine Derivatives in High Optical Purity. Org. Biomol. Chem. 2010, 8, 2016−2019. (218) Wang, C.; Chen, X.-H.; Zhou, S.-M.; Gong, L.-Z. Asymmetric Organocatalytic Formal Double-Arylation of Azomethines for the Synthesis of Highly Enantiomerically Enriched Isoindolines. Chem. Commun. 2010, 46, 1275−1277. (219) Chen, X.-H.; Zhang, W.-Q.; Gong, L.-Z. Asymmetric Organocatalytic Three-Component 1,3-Dipolar Cycloaddition: Control of Stereochemistry via a Chiral Brønsted Acid Activated Dipole. J. Am. Chem. Soc. 2008, 130, 5652−5653. (220) He, L.; Chen, X.-H.; Wang, D.-N.; Luo, S.-W.; Zhang, W.-Q.; Yu, J.; Ren, L.; Gong, L.-Z. Binaphthol-Derived Bisphosphoric Acids Serve as Efficient Organocatalysts for Highly Enantioselective 1,3Dipolar Cycloaddition of Azomethine Ylides to Electron-Deficient Olefins. J. Am. Chem. Soc. 2011, 133, 13504−13518. (221) Chen, X.-H.; Wei, Q.; Luo, S.-W.; Xiao, H.; Gong, L.-Z. Organocatalytic Synthesis of Spiro[pyrrolidin-3,3′-oxindoles] with High Enantiopurity and Structural Diversity. J. Am. Chem. Soc. 2009, 131, 13819−13825. (222) Yu, J.; He, L.; Chen, X.-H.; Song, J.; Chen, W.-J.; Gong, L.-Z. Highly Enantioselective Catalytic 1,3-Dipolar Cycloaddition Involving 2,3-Allenoate Dipolarophiles. Org. Lett. 2009, 11, 4946−4949. (223) Shi, F.; Tao, Z.-L.; Luo, S.-W.; Tu, S.-J.; Gong, L.-Z. ScaffoldInspired Enantioselective Synthesis of Biologically Important Spiro[pyrrolidin-3,2 ′-oxindoles] with Structural Diversity through Catalytic Isatin-Derived 1,3-Dipolar Cycloadditions. Chem. - Eur. J. 2012, 18, 6885−6894. (224) Shi, F.; Zhu, R.-Y.; Liang, X.; Tu, S.-J. Catalytic Asymmetric 1,3-Dipolar Cycloadditions of Alkynes with Isatin-Derived Azomethine Ylides: Enantioselective Synthesis of Spiro[indoline-3,2 ′-pyrrole] Derivatives. Adv. Synth. Catal. 2013, 355, 2447−2458. (225) Shi, F.; Xing, G.-J.; Tan, W.; Zhu, R.-Y.; Tu, S.-J. Enantioselective Construction of 2,5-Dihydropyrrole Skeleton with Quaternary Stereogenic Center via Catalytic Asymmetric 1,3-Dipolar Cycloaddition Involving α-Arylglycine Esters. Org. Biomol. Chem. 2013, 11, 1482−1489. (226) Shi, F.; Zhu, R.-Y.; Dai, W.; Wang, C.-S.; Tu, S.-J. Catalytic Asymmetric Formal [3 + 3] Cycloaddition of an Azomethine Ylide with 3-Indolylmethanol: Enantioselective Construction of a SixMembered Piperidine Framework. Chem. - Eur. J. 2014, 20, 2597− 2604. (227) Zhong, F.; Han, X.; Wang, Y.; Lu, Y. Highly Enantioselective [3 + 2] Annulation of Morita−Baylis−Hillman Adducts Mediated by L-Threonine-Derived Phosphines: Synthesis of 3-Spirocyclopentene-2oxindoles having Two Contiguous Quaternary Centers. Angew. Chem., Int. Ed. 2011, 50, 7837−7841. (228) Wanner, M. J.; van der Haas, R. N. S.; de Cuba, K. R.; van Maarseveen, J. H.; Hiemstra, H. Catalytic Asymmetric Pictet-Spengler Reactions via Sulfenyliminium Ions. Angew. Chem., Int. Ed. 2007, 46, 7485−7487. (229) Kimmel, K. L.; Weaver, J. D.; Lee, M.; Ellman, J. A. Catalytic Enantioselective Protonation of Nitronates Utilizing an Organocatalyst Chiral Only at Sulfur. J. Am. Chem. Soc. 2012, 134, 9058−9061. (230) Č orić, I.; List, B. Asymmetric Spiroacetalization Catalysed by Confined Brønsted Acids. Nature 2012, 483, 315−319. (231) Sun, Z.; Winschel, G. A.; Borovika, A.; Nagorny, P. Chiral Phosphoric Acid-Catalyzed Enantioselective and Diastereoselective Spiroketalizations. J. Am. Chem. Soc. 2012, 134, 8074−8077. 4114


Chemical Reviews

Review

Reactions of 3-Substituted Benzofuran-2(3H)-ones to Nitroolefins Catalyzed by a Bifunctional Tertiary-Amine Thiourea. Org. Biomol. Chem. 2012, 10, 413−420. (253) Pei, Q.-L.; Sun, H.-W.; Wu, Z.-J.; Du, X.-L.; Zhang, X.-M.; Yuan, W.-C. Catalytic Asymmetric 1,6-Michael Addition of Arylthiols to 3-Methyl-4-Nitro-5-Alkenyl-Isoxazoles with Bifunctional Catalysts. J. Org. Chem. 2011, 76, 7849−7859. (254) Wang, C.-J.; Dong, X.-Q.; Zhang, Z.-H.; Xue, Z.-Y.; Teng, H.L. Highly Anti-Selective Asymmetric Nitro-Mannich Reactions Catalyzed by Bifunctional Amine-Thiourea-Bearing Multiple Hydrogen-Bonding Donors. J. Am. Chem. Soc. 2008, 130, 8606−8607. (255) Dong, X.-Q.; Teng, H.-L.; Tong, M.-C.; Huang, H.; Tao, H.-Y.; Wang, C.-J. Organocatalytic Asymmetric Michael Addition of α-Aryl Cyclopentanones to Nitroolefins for Construction of Adjacent Quaternary and Tertiary Stereocenters. Chem. Commun. 2010, 46, 6840−6842. (256) Jia, Z.-X.; Luo, Y.-C.; Cheng, X.-N.; Xu, P.-F.; Gu, Y.-C. Organocatalyzed Michael-Michael Cascade Reaction: Asymmetric Synthesis of Polysubstituted Chromans. J. Org. Chem. 2013, 78, 6488−6494. (257) Duque, M. D. M. S.; Baslé, O.; Génisson, Y.; Plaquevent, J.-C.; Bugaut, X.; Constantieux, T.; Rodriguez, J. Enantioselective Organocatalytic Multicomponent Synthesis of 2,6-Diazabicyclo[2.2.2]octanones. Angew. Chem., Int. Ed. 2013, 52, 14143−14146. (258) Sundén, H.; Ibrahem, I.; Zhao, G.-L.; Eriksson, L.; Córdova, A. Catalytic Enantioselective Domino Oxa-Michael/Aldol Condensations: Asymmetric Synthesis of Benzopyran Derivatives. Chem. - Eur. J. 2007, 13, 574−581. (259) Hong, L.; Sun, W.; Liu, C.; Wang, L.; Wang, R. Asymmetric Organocatalytic N-Alkylation of Indole-2-Carbaldehydes with α,βUnsaturated Aldehydes: One-Pot Synthesis of Chiral Pyrrolo[1,2a]indole-2-Carbaldehydes. Chem. - Eur. J. 2010, 16, 440−444. (260) Jian, T.-Y.; He, L.; Tang, C.; Ye, S. N-Heterocyclic Carbene Catalysis: Enantioselective Formal [2 + 2] Cycloaddition of Ketenes and N-Sulfinylanilines. Angew. Chem., Int. Ed. 2011, 50, 9104−9107. (261) Zhu, Z.-Q.; Zheng, X.-L.; Jiang, N.-F.; Wan, X.; Xiao, J.-C. Chiral N-Heterocyclic Carbene Catalyzed Annulation of α,βUnsaturated Aldehydes with 1,3-Dicarbonyls. Chem. Commun. 2011, 47, 8670−8672. (262) DiRocco, D. A.; Rovis, T. Catalytic Asymmetric Cross-AzaBenzoin Reactions of Aliphatic Aldehydes with N-Boc-Protected Imines. Angew. Chem., Int. Ed. 2012, 51, 5904−5906. (263) Thai, K.; Langdon, S. M.; Bilodeau, F.; Gravel, M. Highly Chemo- and Enantioselective Cross-Benzoin Reaction of Aliphatic Aldehydes and α-Ketoesters. Org. Lett. 2013, 15, 2214−2217. (264) Atienza, R. L.; Roth, H. S.; Scheidt, K. A. N-Heterocyclic Carbene-Catalyzed Rearrangements of Vinyl Sulfones. Chem. Sci. 2011, 2, 1772−1776. (265) Iwahana, S.; Iida, H.; Yashima, E. Oxidative Esterification, Thioesterification, and Amidation of Aldehydes by a Two-Component Organocatalyst System Using a Chiral N-Heterocyclic Carbene and Redox-Active Riboflavin. Chem. - Eur. J. 2011, 17, 8009−8013. (266) Roy, S. J. S.; Mukherjee, S. Enantioselective Desymmetrization of Prochiral 1,3-Dinitropropanes via Organocatalytic Allylic Alkylation. Chem. Commun. 2014, 50, 121−123. (267) Huang, X.; Peng, J.; Dong, L.; Chen, Y.-C. Asymmetric Assembly of 2-Oxindole and α-Angelica Lactone Units to Construct Vicinal Quaternary Chiral Centers. Chem. Commun. 2012, 48, 2439− 2441. (268) Yang, W.; Tan, D.; Li, L.; Han, Z.; Yan, L.; Huang, K.-W.; Tan, C.-H.; Jiang, Z. Direct Asymmetric Allylic Alkenylation of NItaconimides with Morita−Baylis−Hillman Carbonates. J. Org. Chem. 2012, 77, 6600−6607. (269) Zhang, X.-N.; Deng, H.-P.; Huang, L.; Wei, Y.; Shi, M. Phosphine-Catalyzed Asymmetric [4 + 1] Annulation of Morita− Baylis−Hillman Carbonates with Dicyano-2-Methylenebut-3-Enoates. Chem. Commun. 2012, 48, 8664−8666. (270) Denis, J.-B.; Masson, G.; Retailleau, P.; Zhu, J. Cinchona Alkaloid Amide Catalyzed Enantioselective Formal [2 + 2] Cyclo-

additions of Allenoates and Imines: Synthesis of 2,4-Disubstituted Azetidines. Angew. Chem., Int. Ed. 2011, 50, 5356−5360. (271) Pei, C.-K.; Shi, M. Asymmetric Cyclization Reactions of Allenoates with Imines or α,β-Unsaturated Ketones Catalyzed by Organocatalysts Derived from Cinchona Alkaloids. Chem. - Eur. J. 2012, 18, 6712−6716. (272) Uraguchi, D.; Koshimoto, K.; Miyake, S.; Ooi, T. Chiral Ammonium Bines as Ionic Nucleophilic Catalysts. Angew. Chem., Int. Ed. 2010, 49, 5567−5569. (273) Uraguchi, D.; Oyaizu, K.; Ooi, T. Nitroolefins as a Nucleophilic Component for Highly Stereoselective Aza Henry Reaction under the Catalysis of Chiral Ammonium Bines. Chem. Eur. J. 2012, 18, 8306−8309. (274) Zhang, Z.; Xie, F.; Jia, J.; Zhang, W. Chiral Bicycle Imidazole Nucleophilic Catalysts: Rational Design, Facile Synthesis, and Successful Application in Asymmetric Steglich Rearrangement. J. Am. Chem. Soc. 2010, 132, 15939−15941. (275) Wang, M.; Zhang, Z.; Liu, S.; Xie, F.; Zhang, W. Enantioselective Black Rearrangement Catalyzed by Chiral Bicyclic Imidazole. Chem. Commun. 2014, 50, 1227−1230. (276) Storer, R. I.; Carrera, D. E.; Ni, Y.; MacMillan, D. W. C. Enantioselective Organocatalytic Reductive Amination. J. Am. Chem. Soc. 2006, 128, 84−86. (277) Wakchaure, V. N.; Zhou, J.; Hoffmann, S.; List, B. Catalytic Asymmetric Reductive Amination of α-Branched Ketones. Angew. Chem., Int. Ed. 2010, 49, 4612−4614. (278) Zhou, J.; List, B. Organocatalytic Asymmetric Reaction Cascade to Substituted Cyclohexylamines. J. Am. Chem. Soc. 2007, 129, 7498−7499. (279) Enders, D.; Liebich, J. X.; Raabe, G. Organocatalytic Asymmetric Synthesis of Trans-1,3-Disubstituted Tetrahydroisoquinolines via a Reductive Amination/Aza-Michael Sequence. Chem. - Eur. J. 2010, 16, 9763−9766. (280) Lu, M.; Lu, Y.; Zhu, D.; Zeng, X.; Li, X.; Zhong, G. Chiral Brønsted Acid Catalyzed Enantioselective α-Aminoxylation of Enecarbamates. Angew. Chem., Int. Ed. 2010, 49, 8588−8592. (281) Kim, J. H.; Č orić, I.; Palumbo, C.; List, B. Resolution of Diols via Catalytic Asymmetric Acetalization. J. Am. Chem. Soc. 2015, 137, 1778−1781. (282) Saito, K.; Shibata, Y.; Yamanaka, M.; Akiyama, T. Chiral Phosphoric Acid-Catalyzed Oxidative Kinetic Resolution of Indolines Based on Transfer Hydrogenation to Imines. J. Am. Chem. Soc. 2013, 135, 11740−11743. (283) Vellalath, S.; Č orić, I.; List, B. N-Phosphinyl Phosphoramide-A Chiral Brønsted Acid Motif for the Direct Asymmetric N,OAcetalization of Aldehydes. Angew. Chem., Int. Ed. 2010, 49, 9749− 9752. (284) Kano, T.; Yurino, T.; Maruoka, K. Organocatalytic Asymmetric Synthesis of Propargylamines with Two Adjacent Stereocenters: Mannich-Type Reactions of In Situ Generated C-Alkynyl Imines with β-Keto Esters. Angew. Chem., Int. Ed. 2013, 52, 11509−11512. (285) Shi, F.; Xing, G.-J.; Tao, Z.-L.; Luo, S.-W.; Tu, S.-J.; Gong, L.Z. An Asymmetric Organocatalytic Povarov Reaction with 2Hydroxystyrenes. J. Org. Chem. 2012, 77, 6970−6979. (286) Wang, S.-G.; Han, L.; Zeng, M.; Sun, F.-L.; Zhang, W.; You, S.L. Enantioselective Synthesis of Fluorene Derivatives by Chiral NTriflyl Phosphoramide Catalyzed Double Friedel−Crafts Alkylation Reaction. Org. Biomol. Chem. 2012, 10, 3202−3209. (287) Ren, H.; Wulff, W. D. Direct Catalytic Asymmetric Aminoallylation of Aldehydes: Synergism of Chiral and Nonchiral Brønsted Acids. J. Am. Chem. Soc. 2011, 133, 5656−5659. (288) Zhou, F.; Ding, M.; Liu, Y.-L.; Wang, C.-H.; Ji, C.-B.; Zhang, Y.-Y.; Zhou, J. Organocatalytic Asymmetric α-Amination of Unprotected 3-Aryl and 3-Aliphatic Substituted Oxindoles using Di-tertButyl Azodicarboxylate. Adv. Synth. Catal. 2011, 353, 2945−2952. (289) Ding, M.; Zhou, F.; Liu, Y.-L.; Wang, C.-H.; Zhao, X.-L.; Zhou, J. Cinchona Alkaloid-Based Phosphoramide Catalyzed Highly Enantioselective Michael Addition of Unprotected 3-Substituted Oxindoles to Nitroolefins. Chem. Sci. 2011, 2, 2035−2039. 4115


Chemical Reviews

Review

(308) Wu, X.; Li, Y.; Wang, C.; Zhou, L.; Lu, X.; Sun, J. Chiral Lewis Base Catalyzed Highly Enantioselective Reduction of N-Alkyl βEnamino Esters with Trichlorosilane and Water. Chem. - Eur. J. 2011, 17, 2846−2848. (309) Liu, X.-W.; Yan, Y.; Wang, Y.-Q.; Wang, C.; Sun, J. Highly Enantioselective Reduction of β-Amino Nitroolefins with a Simple NSulfinyl Urea as Bifunctional Catalyst. Chem. - Eur. J. 2012, 18, 9204− 9207. (310) Xiao, Y.-C.; Wang, C.; Yao, Y.; Sun, J.; Chen, Y.-C. Direct Asymmetric Hydrosilylation of Indoles: Combined Lewis Base and Brønsted Acid Activation. Angew. Chem., Int. Ed. 2011, 50, 10661− 10664. (311) Zhou, Y.; Shan, Z. Chiral diols: A New Class of Additives for Direct Aldol Reaction Catalyzed by L-Proline. J. Org. Chem. 2006, 71, 9510−9512. (312) Reis, Ö .; Eymur, S.; Reis, B.; Demir, A. S. Direct Enantioselective Aldol Reactions Catalyzed by a Proline-Thiourea Host-Guest Complex. Chem. Commun. 2009, 1088−1090. (313) Demir, A. S.; Eymur, S. Self-assembly of Organocatalysts for the Enantioselective Michael Addition of Aldehydes to Nitroalkenes. Tetrahedron: Asymmetry 2010, 21, 112−115. (314) Ma, G.; Bartoszewicz, A.; Ibrahem, I.; Córdova, A. Highly Enantioselective Co-Catalytic Direct Aldol Reactions by Combination of Hydrogen-Bond Donating and Acyclic Amino Acid Catalysts. Adv. Synth. Catal. 2011, 353, 3114−3122. (315) Companyó, X.; Valero, G.; Crovetto, L.; Moyano, A.; Rios, R. Highly Enantio- and Diastereoselective Organocatalytic Desymmetrization of Prochiral Cyclohexanones by Simple Direct Aldol Reaction Catalyzed by Proline. Chem. - Eur. J. 2009, 15, 6564−6568. (316) El-Hamdouni, N.; Companyó, X.; Rios, R.; Moyano, A. Substrate-Dependent Nonlinear Effects in Proline-Thiourea-Catalyzed Aldol Reactions: Unraveling the Role of the Thiourea Co-Catalyst. Chem. - Eur. J. 2010, 16, 1142−1148. (317) Wang, Y.; Yu, T.-Y.; Zhang, H.-B.; Luo, Y.-C.; Xu, P.-F. Hydrogen-Bond-Mediated Supramolecular Iminium Ion Catalysis. Angew. Chem., Int. Ed. 2012, 51, 12339−12342. (318) Gu, Y.; Wang, Y.; Yu, T.-Y.; Liang, Y.-M.; Xu, P.-F. Rationally Designed Multifunctional Supramolecular Iminium Catalysis: Direct Vinylogous Michael Addition of Unmodified Linear Dienol Substrates. Angew. Chem., Int. Ed. 2014, 53, 14128−14131. (319) Talavera, G.; Reyes, E.; Vicario, J. L.; Carrillo, L. Cooperative Dienamine/Hydrogen-Bonding Catalysis: Enantioselective Formal [2 + 2] Cycloaddition of Enals with Nitroalkenes. Angew. Chem., Int. Ed. 2012, 51, 4104−4107. (320) Burns, N. Z.; Witten, M. R.; Jacobsen, E. N. Dual Catalysis in Enantioselective Oxidopyrylium-Based [5 + 2] Cycloadditions. J. Am. Chem. Soc. 2011, 133, 14578−14581. (321) Witten, M. R.; Jacobsen, E. N. Catalytic Asymmetric Synthesis of 8-Oxabicyclooctanes by Intermolecular [5 + 2] Pyrylium Cycloadditions. Angew. Chem., Int. Ed. 2014, 53, 5912−5916. (322) Rubush, D. M.; Morges, M. A.; Rose, B. J.; Thamm, D. H.; Rovis, T. An Asymmetric Synthesis of 1,2,4-Trioxane Anticancer Agents via Desymmetrization of Peroxyquinols through a Brønsted Acid Catalysis Cascade. J. Am. Chem. Soc. 2012, 134, 13554−13557. (323) Martínez, A.; Webber, M. J.; Müller, S.; List, B. Versatile Access to Chiral Indolines by Catalytic Asymmetric Fischer Indolization. Angew. Chem., Int. Ed. 2013, 52, 9486−9490. (324) Müller, S.; Webber, M. J.; List, B. The Catalytic Asymmetric Fischer Indolization. J. Am. Chem. Soc. 2011, 133, 18534−18537. (325) Kötzner, L.; Webber, M. J.; Martínez, A.; De Fusco, C.; List, B. Asymmetric Catalysis on the Nanoscale: The Organocatalytic Approach to Helicenes. Angew. Chem., Int. Ed. 2014, 53, 5202−5205. (326) Huang, S.; Kötzner, L.; De, C. K.; List, B. Catalytic Asymmetric Dearomatizing Redox Cross Coupling of Ketones with Aryl Hydrazines Giving 1,4-Diketones. J. Am. Chem. Soc. 2015, 137, 3446−3449. (327) Hatano, M.; Goto, Y.; Izumiseki, A.; Akakura, M.; Ishihara, K. Boron Tribromide-Assisted Chiral Phosphoric Acid Catalyst for a

(290) Wang, J.; Liu, X.; Dong, S.; Lin, L.; Feng, X. Asymmetric Organocatalytic Cyclopropanation of Cinnamone Derivatives with Stabilized Sulfonium Ylides. J. Org. Chem. 2013, 78, 6322−6327. (291) Aratake, S.; Itoh, T.; Okano, T.; Nagae, N.; Sumiya, T.; Shoji, M.; Hayashi, Y. Highly Diastereo- and Enantioselective Direct Aldol Reactions of Aldehydes and Ketones Catalyzed by Siloxyproline in the Presence of Water. Chem. - Eur. J. 2007, 13, 10246−10256. (292) Hayashi, Y.; Aratake, S.; Itoh, T.; Okano, T.; Sumiya, T.; Shoji, M. Dry and Wet Prolines for Asymmetric Organic Solvent-Free Aldehyde-Aldehyde and Aldehyde-Ketone Aldol Reactions. Chem. Commun. 2007, 957−959. (293) Córdova, A.; Zou, W.; Dziedzic, P.; Ibrahem, I.; Reyes, E.; Xu, Y. Direct Asymmetric Intermolecular Aldol Reactions Catalyzed by Amino Acids and Small Peptides. Chem. - Eur. J. 2006, 12, 5383−5397. (294) Ibrahem, I.; Zou, W.; Xu, Y.; Córdova, A. Amino AcidCatalyzed Asymmetric Carbohydrate Formation: Organocatalytic One-step de Novo Synthesis of Keto and Amino Sugars. Adv. Synth. Catal. 2006, 348, 211−222. (295) Montroni, E.; Sanap, S. P.; Lombardo, M.; Quintavalla, A.; Trombini, C.; Dhavale, D. D. A New Robust and Efficient Ion-Tagged Proline Catalyst Carrying an Amide Spacer for the Asymmetric Aldol Reaction. Adv. Synth. Catal. 2011, 353, 3234−3240. (296) Nakamura, S.; Hara, N.; Nakashima, H.; Kubo, K.; Shibata, N.; Toru, T. Enantioselective Synthesis of (R)-Convolutamydine A with New N-Heteroarylsulfonylprolinamides. Chem. - Eur. J. 2008, 14, 8079−8081. (297) Hara, N.; Nakamura, S.; Shibata, N.; Toru, T. First Enantioselective Synthesis of (R)-Convolutamydine B and E with N(Heteroarenesulfonyl)prolinamides. Chem. - Eur. J. 2009, 15, 6790− 6793. (298) Chen, X.-H.; Luo, S.-W.; Tang, Z.; Cun, L.-F.; Mi, A.-Q.; Jiang, Y.-Z.; Gong, L.-Z. Organocatalyzed Highly Enantioselective Direct Aldol Reactions of Aldehydes with Hydroxyacetone and Fluoroacetone in Aqueous Media: The Use of Water to Control Regioselectivity. Chem. - Eur. J. 2007, 13, 689−701. (299) Xue, F.; Zhang, S.; Duan, W.; Wang, W. A Novel Bifunctional Sulfonamide Primary Amine-Catalyzed Enantioselective Conjugate Addition of Ketones to Nitroolefins. Adv. Synth. Catal. 2008, 350, 2194−2198. (300) Alemán, J.; Cabrera, S.; Maerten, E.; Overgaard, J.; Jørgensen, K. A. Asymmetric Organocatalytic α-Arylation of Aldehydes. Angew. Chem., Int. Ed. 2007, 46, 5520−5523. (301) Han, Bo.; Li, J.-L.; Ma, C.; Zhang, S.-J.; Chen, Y.-C. Organocatalytic Asymmetric Inverse-Electron-Demand Aza-Diels− Alder Reaction of N-Sulfonyl-1-Aza-1,3-Butadienes and Aldehydes. Angew. Chem., Int. Ed. 2008, 47, 9971−9974. (302) Vicario, J. L.; Reboredo, S.; Badía, D.; Carrillo, L. Organocatalytic Enantioselective [3 + 2] Cycloaddition of Azomethine Ylides and α,β-Unsaturated Aldehydes. Angew. Chem., Int. Ed. 2007, 46, 5168−5170. (303) Tsakos, M.; Elsegood, M. R. J.; Kokotos, C. G. Organocatalytic Asymmetric Domino Michael-Henry Reaction for the Synthesis of Substituted Bicyclo[3.2.1]octan-2-Ones. Chem. Commun. 2013, 49, 2219−2221. (304) Aroyan, C. E.; Miller, S. Enantioselective Rauhut-currier Reactions Promoted by Protected Cysteine. J. Am. Chem. Soc. 2007, 129, 256−257. (305) Lalonde, M. P.; Chen, Y.; Jacobsen, E. N. A Chiral Primary Amine Thiourea Catalyst for the Highly Enantioselective Direct Conjugate Addition of α,α-Disubstituted Aldehydes to Nitroalkenes. Angew. Chem., Int. Ed. 2006, 45, 6366−6370. (306) Huang, H.; Jacobsen, E. N. Highly Enantioselective Direct Conjugate Addition of Ketones to Nitroalkenes Promoted by a Chiral Primary Amine-Thiourea Catalyst. J. Am. Chem. Soc. 2006, 128, 7170− 7171. (307) Brown, A. R.; Kuo, W.-H.; Jacobsen, E. N. Enantioselective Catalytic α-Alkylation of Aldehydes via an SN1 Pathway. J. Am. Chem. Soc. 2010, 132, 9286−9288. 4116


Chemical Reviews

Review

Highly Enantioselective Diels−Alder Reaction of 1,2-Dihydropyridines. J. Am. Chem. Soc. 2015, 137, 13472. (328) Mittal, N.; Sun, D. X.; Seidel, D. Conjugate-Base-Stabilized Brønsted Acids: Catalytic Enantioselective Pictet-Spengler Reactions with Unmodified Tryptamine. Org. Lett. 2014, 16, 1012−1015. (329) Wakchaure, V. N.; Kaib, P. S. J.; Leutzsch, M.; List, B. Disulfonimide-Catalyzed Asymmetric Reduction of N-Alkyl Imines. Angew. Chem., Int. Ed. 2015, 54, 11852−11856. (330) Liu, H.; Jiang, G.; Pan, X.; Wan, X.; Lai, Y.; Ma, D.; Xie, W. Highly Asymmetric Bromocyclization of Tryptophol: Unexpected Accelerating Effect of DABCO-Derived Bromine Complex. Org. Lett. 2014, 16, 1908−1911. (331) Xie, W.; Jiang, G.; Liu, H.; Hu, J.; Pan, X.; Zhang, H.; Wan, X.; Lai, Y.; Ma, D. Highly Enantioselective Bromocyclization of Tryptamines and Its Application in the Synthesis of (−)-Chimonanthine. Angew. Chem., Int. Ed. 2013, 52, 12924−12927. (332) Uraguchi, D.; Tsutsumi, R.; Ooi, T. Catalytic Asymmetric Oxidation of N-Sulfonyl Imines with Hydrogen Peroxide-Trichloroacetonitrile System. J. Am. Chem. Soc. 2013, 135, 8161−8164. (333) Uraguchi, D.; Tsutsumi, R.; Ooi, T. Catalytic Asymmetric Payne Oxidation under the Catalysis of P-spiro Chiral Triaminoiminophosphorane: Application to the Synthesis of N-Sulfonyl Oxaziridines. Tetrahedron 2014, 70, 1691−1701. (334) Shirakawa, S.; Yamamoto, K.; Kitamura, M.; Ooi, T.; Maruoka, K. Dramatic Rate Enhancement of Asymmetric Phase-TransferCatalyzed Alkylations. Angew. Chem., Int. Ed. 2005, 44, 625−628. (335) Vora, H. U.; Rovis, T. Nucleophilic Carbene and HOAt Relay Catalysis in an Amide Bond Coupling: An Orthogonal Peptide Bond Forming Reaction. J. Am. Chem. Soc. 2007, 129, 13796−13797. (336) Wheeler, P.; Vora, H. U.; Rovis, T. Asymmetric NHCCatalyzed Synthesis of α-Fluoroamides from Readily Accessible αFluoroenals. Chem. Sci. 2013, 4, 1674−1679. (337) West, T. H.; Daniels, D. S. B.; Slawin, A. M. Z.; Smith, A. D. An Isothiourea-Catalyzed Asymmetric [2,3]-Rearrangement of Allylic Ammonium Ylides. J. Am. Chem. Soc. 2014, 136, 4476−4479. (338) Lin, S.; Deiana, L.; Zhao, G.-L.; Sun, J.; Córdova, A. Dynamic One-Pot Three-Component Catalytic Asymmetric Transformation by Combination of Hydrogen-Bond-Donating and Amine Catalysts. Angew. Chem., Int. Ed. 2011, 50, 7624−7630. (339) Juhl, K.; Jørgensen, K. A. The First Organocatalytic Enantioselective Inverse-Electron-Demand Hetero-Diels−Alder Reaction. Angew. Chem., Int. Ed. 2003, 42, 1498−1501. (340) Zhong, C.; Chen, Y.; Petersen, J. L.; Akhmedov, N. G.; Shi, X. Enantioselective Intermolecular Crossed-Conjugate Additions between Nitroalkenes and α,β-Enals through a Dual Activation Strategy. Angew. Chem., Int. Ed. 2009, 48, 1279−1282. (341) Sano, D.; Nagata, K.; Itoh, T. Catalytic Asymmetric Hydroxylation of Oxindoles by Molecular Oxygen Using a PhaseTransfer Catalyst. Org. Lett. 2008, 10, 1593−1595. (342) Denmark, S. E.; Burk, M. T. Enantioselective Bromocycloetherification by Lewis Base/Chiral Brønsted Acid Cooperative Catalysis. Org. Lett. 2012, 14, 256−259. (343) Taylor, M. S.; Jacobsen, E. N. Highly Enantioselective Catalytic Acyl-Pictet-Spengler reactions. J. Am. Chem. Soc. 2004, 126, 10558− 10559. (344) Taylor, M. S.; Tokunaga, N.; Jacobsen, E. N. Enantioselective Thiourea-Catalyzed Acyl-Mannich Reactions of Isoquinolines. Angew. Chem., Int. Ed. 2005, 44, 6700−6704. (345) Raheem, I. T.; Thiara, P. S.; Peterson, E. A.; Jacobsen, E. N. Enantioselective Pictet-Spengler-Type Cyclizations of Hydroxylactams: H-Bond Donor Catalysis by Anion Binding. J. Am. Chem. Soc. 2007, 129, 13404−13405. (346) Peterson, E. A.; Jacobsen, E. N. Enantioselective, ThioureaCatalyzed Intermolecular Addition of Indoles to Cyclic N-Acyl Iminium Ions. Angew. Chem., Int. Ed. 2009, 48, 6328−6331. (347) Nakamura, S.; Takahashi, S.; Nakane, D.; Masuda, H. Organocatalytic Enantioselective Addition of Thiols to Ketimines Derived from Isatins. Org. Lett. 2015, 17, 106−109.

(348) Cai, Q.; Liang, X.-W.; Wang, S.-G.; You, S.-L. An Olefin Isomerization/Asymmetric Pictet-Spengler Cascade via Sequential Catalysis of Ruthenium Alkylidene and Chiral Phosphoric Acid. Org. Biomol. Chem. 2013, 11, 1602−1605. (349) Louie, J.; Grubbs, R. H. Metathesis of Electron-Rich Olefins: Structure and Reactivity of Electron-Rich Carbene Complexes. Organometallics 2002, 21, 2153−2164. (350) Trost, B. M.; Fandrick, D. R. Dynamic Kinetic Asymmetric Cycloadditions of Isocyanates to Vinylaziridines. J. Am. Chem. Soc. 2003, 125, 11836−11837. (351) Trost, B. M.; Shen, H. C.; Dong, L.; Surivet, J.-P.; Sylvain, C. Synthesis of Chiral Chromans by the Pd-catalyzed Asymmetric Allylic Alkylation (AAA): Scope, Mechanism, and Applications. J. Am. Chem. Soc. 2004, 126, 11966−11983. (352) Hatano, M.; Hattori, Y.; Furuya, Y.; Ishihara, K. Chiral Lanthanum(III)-Binaphthyldisulfonate Complexes for Catalytic Enantioselective Strecker Reaction. Org. Lett. 2009, 11, 2321−2324. (353) Kobayashi, S.; Xu, P.; Endo, T.; Ueno, M.; Kitanosono, T. Chiral Copper(II)-Catalyzed Enantioselective Boron Conjugate Additions to α,β-Unsaturated Carbonyl Compounds in Water. Angew. Chem., Int. Ed. 2012, 51, 12763−12766. (354) Breitler, S.; Carreira, E. M. Formaldehyde N,N-Dialkylhydrazones as Neutral Formyl Anion Equivalents in Iridium-Catalyzed Asymmetric Allylic Substitution. J. Am. Chem. Soc. 2015, 137, 5296− 5299. (355) Kong, J.-R.; Ngai, M.-Y.; Krische, M. J. Highly Enantioselective Direct Reductive Coupling of Conjugated Alkynes and α-Ketoesters via Rhodium-Catalyzed Asymmetric Hydrogenation. J. Am. Chem. Soc. 2006, 128, 718−719. (356) Hong, Y.-T.; Cho, C.-W.; Skucas, E.; Krische, M. J. Enantioselective Reductive Coupling of 1,3-Enynes to Glyoxalates Mediated by Hydrogen: Asymmetric Synthesis of β,γ-Unsaturated αHydroxy Esters. Org. Lett. 2007, 9, 3745−3748. (357) Komanduri, V.; Krische, M. J. Enantioselective Reductive Coupling of 1,3-Enynes to Heterocyclic Aromatic Aldehydes and Ketones via Rhodium-Catalyzed Asymmetric Hydrogenation: Mechanistic Insight into the Role of Brønsted Acid Additives. J. Am. Chem. Soc. 2006, 128, 16448−16449. (358) Rhee, J. U.; Krische, M. J. Highly Enantioselective Reductive Cyclization of Acetylenic Aldehydes via Rhodium Catalyzed Asymmetric Hydrogenation. J. Am. Chem. Soc. 2006, 128, 10674− 10675. (359) Ollevier, T.; Plancq, B. Highly Enantioselective Mukaiyama Aldol Reaction in Aqueous Conditions Using a Chiral Iron(II) bipyridine Catalyst. Chem. Commun. 2012, 48, 2289−2291. (360) Lin, W.; Cao, T.; Fan, W.; Han, Y.; Kuang, J.; Luo, H.; Miao, B.; Tang, X.; Yu, Q.; Yuan, W.; Zhang, J.; Zhu, C.; Ma, S. Enantioselective Double Manipulation of Tetrahydroisoquinolines with Terminal Alkynes and Aldehydes under Copper(I) Catalysis. Angew. Chem., Int. Ed. 2014, 53, 277−281. (361) Cherney, A. H.; Kadunce, N. T.; Reisman, S. E. Catalytic Asymmetric Reductive Acyl Cross-Coupling: Synthesis of Enantioenriched Acyclic α,α-Disubstituted Ketones. J. Am. Chem. Soc. 2013, 135, 7442−7445. (362) Hui, Y.; Zhang, Q.; Jiang, J.; Lin, L.; Liu, X.; Feng, X. Highly Efficient Asymmetric Synthesis of 3-Indolyl(hydroxy)acetates via Friedel−Crafts Alkylation of Indoles. J. Org. Chem. 2009, 74, 6878− 6880. (363) Kim, I. S.; Ngai, M.-Y.; Krische, M. J. Enantioselective IridiumCatalyzed Carbonyl Allylation from the Alcohol or Aldehyde Oxidation Level via Transfer Hydrogenative Coupling of Allyl Acetate: Departure from Chirally Modified Allyl Metal Reagents in Carbonyl Addition. J. Am. Chem. Soc. 2008, 130, 14891−14899. (364) Legros, J.; Bolm, C. Investigations on the Iron-Catalyzed Asymmetric Sulfide Oxidation. Chem. - Eur. J. 2005, 11, 1086−1092. (365) Legros, J.; Bolm, C. Highly Enantioselective Iron-Catalyzed Sulfide Oxidation with Aqueous Hydrogen Peroxide under Simple Reaction Conditions. Angew. Chem., Int. Ed. 2004, 43, 4225−4228. 4117


Chemical Reviews

Review

and Application in Asymmetric Hydrogenation. J. Org. Chem. 2008, 73, 775−784. (385) Li, S.; Zhu, S.-F.; Zhang, C.-M.; Song, S.; Zhou, Q.-L. IridiumCatalyzed Enantioselective Hydrogenation of α,β-Unsaturated Carboxylic Acids. J. Am. Chem. Soc. 2008, 130, 8584−8585. (386) Song, S.; Zhu, S.-F.; Yang, S.; Li, S.; Zhou, Q.-L. Enantioselective Iridium-Catalyzed Hydrogenation of β,γ-Unsaturated Carboxylic Acids: An Efficient Approach to Chiral 4-Alkyl-4-Aryl Butanoic Acids. Angew. Chem., Int. Ed. 2012, 51, 2708−2711. (387) Sun, X.; Zhou, L.; Wang, C.-J.; Zhang, X. Rh-catalyzed Highly Enantioselective Synthesis of 3-Arylbutanoic Acids. Angew. Chem., Int. Ed. 2007, 46, 2623−2626. (388) Yamamoto, K.; Ikeda, K.; Yin, L. K. Optimization of Asymmetric Hydrogenation of 3-Phenyl-3-Butenoic Acid-Catalyzed by Rhodium(I)-4,5-Bis[(diphenylphosphino)methyl]-2,2-Dimethyldioxolane (diop). J. Organomet. Chem. 1989, 370, 319−332. (389) Yin, L.; Takada, H.; Kumagai, N.; Shibasaki, M. Direct Catalytic Asymmetric Vinylogous Mannich-Type Reaction of γButenolides with Ketimines. Angew. Chem., Int. Ed. 2013, 52, 7310− 7313. (390) Ma, K.; You, J. Rational Design of Sterically and Electronically Easily Tunable Chiral Bisimidazolines and Their Applications in Dual Lewis Acid/Brønsted Base Catalysis for Highly Enantioselective Nitroaldol (Henry) Reactions. Chem. - Eur. J. 2007, 13, 1863−1871. (391) Zhao, J.; Liu, X.; Luo, W.; Xie, M.; Lin, L.; Feng, X. Asymmetric Synthesis of β-Amino Nitriles through a ScIII-Catalyzed Three-Component Mannich Reaction of Silyl Ketene Imines. Angew. Chem., Int. Ed. 2013, 52, 3473−3477. (392) Zhao, D.; Mao, L.; Wang, Y.; Yang, D.; Zhang, Q.; Wang, R. Catalytic Asymmetric Hydrophosphinylation of α,β-Unsaturated NAcylpyrroles: Application of Dialkyl Phosphine Oxides in Enantioselective Synthesis of Chiral Phosphine Oxides or Phosphines. Org. Lett. 2010, 12, 1880−1882. (393) Zhao, D.; Mao, L.; Yang, D.; Wang, R. Zinc-Mediated Asymmetric Additions of Dialkylphosphine Oxides to α,β-Unsaturated Ketones and N-Sulfinylimines. J. Org. Chem. 2010, 75, 6756−6763. (394) Zhao, D.; Mao, L.; Wang, L.; Yang, D.; Wang, R. Catalytic Asymmetric Construction of Tetrasubstituted Carbon Stereocenters by Conjugate Addition of Dialkyl Phosphine Oxides to β,βDisubstituted α,β-Unsaturated Carbonyl Compounds. Chem. Commun. 2012, 48, 889−891. (395) Jin, W.; Li, X.; Wan, B. A Highly Diastereo- and Enantioselective Copper(I)-Catalyzed Henry Reaction Using a Bis(sulfonamide)-Diamine Ligand. J. Org. Chem. 2011, 76, 484−491. (396) Lang, K.; Park, J.; Hong, S. Urea/Transition-Metal Cooperative Catalyst for Anti-Selective Asymmetric Nitroaldol Reactions. Angew. Chem., Int. Ed. 2012, 51, 1620−1624. (397) Cahard, E.; Male, H. P. J.; Tissot, M.; Gaunt, M. J. Enantioselective and Regiodivergent Copper-Catalyzed Electrophilic Arylation of Allylic Amides with Diaryliodonium Salts. J. Am. Chem. Soc. 2015, 137, 7986−7989. (398) Xu, Y.; Kaneko, K.; Kanai, M.; Shibasaki, M.; Matsunaga, S. Regiodivergent Kinetic Resolution of Terminal and Internal RacAziridines with Malonates under Dinuclear Schiff Base Catalysis. J. Am. Chem. Soc. 2014, 136, 9190−9194. (399) Ferraris, D.; Drury, W. J., III; Cox, C.; Lectka, T. ″Orthogonal″ Lewis acids: Catalyzed Ring Opening and Rearrangement of Acylaziridines. J. Org. Chem. 1998, 63, 4568−4569. (400) Södergren, M. J.; Bertilsson, S. K.; Andersson, P. G. Allylic Alcohols via Catalytic Asymmetric Epoxide Rearrangement. J. Am. Chem. Soc. 2000, 122, 6610−6618. (401) Kiener, C. A.; Shu, C.; Incarvito, C.; Hartwig, J. F. Identification of an Activated Catalyst in the Iridium-catalyzed Allylic Amination and Etherification. Increased Rates, Scope, and Selectivity. J. Am. Chem. Soc. 2003, 125, 14272−14273. (402) Ohmura, T.; Hartwig, J. F. Regio- and Enantioselective Allylic Amination of Achiral Allylic Esters Catalyzed by an Iridiumphosphoramidite Complex. J. Am. Chem. Soc. 2002, 124, 15164− 15165.

(366) White, M. C.; Doyle, A. G.; Jacobsen, E. N. A Synthetically Useful, Self-Assembling MMO Mimic System for Catalytic Alkene Epoxidation with Aqueous H2O2. J. Am. Chem. Soc. 2001, 123, 7194− 7195. (367) Mas-Ballesté, R., Jr; Que, L. Iron-Catalyzed Olefin Epoxidation in the Presence of Acetic Acid: Insights into the Nature of the MetalBased Oxidant. J. Am. Chem. Soc. 2007, 129, 15964−15972. (368) Wang, B.; Wang, S.; Xia, C.; Sun, W. Highly Enantioselective Epoxidation of Multisubstituted Enones Catalyzed by Non-Heme Iron Catalysts. Chem. - Eur. J. 2012, 18, 7332−7335. (369) Cussó, O.; Garcia-Bosch, I.; Ribas, X.; Lloret-Fillol, J.; Costas, M. Asymmetric Epoxidation with H2O2 by Manipulating the Electronic Properties of Non-Heme Iron Catalysts. J. Am. Chem. Soc. 2013, 135, 14871−14878. (370) Lyakin, O. Y.; Ottenbacher, R. V.; Bryliakov, K. P.; Talsi, E. P. Asymmetric Epoxidations with H2O2 on Fe and Mn Aminopyridine Catalysts: Probing the Nature of Active Species by Combined Electron Paramagnetic Resonance and Enantioselectivity Study. ACS Catal. 2012, 2, 1196−1202. (371) Lyakin, O. Y.; Bryliakov, K. P.; Britovsek, G. J. P.; Talsi, E. P. EPR Spectroscopic Trapping of the Active Species of Nonheme IronCatalyzed Oxidation. J. Am. Chem. Soc. 2009, 131, 10798−10799. (372) Prat, I.; Mathieson, J. S.; Güell, M.; Ribas, X.; Luis, J. M.; Cronin, L.; Costas, M. Observation of Fe(v)O Using Variabletemperature Mass Spectrometry and Its Enzyme-like C-H and CC Oxidation Reactions. Nat. Chem. 2011, 3, 788−793. (373) Yuan, Y.; Long, J.; Sun, J.; Ding, K. Dramatically Synergetic Effect of Carboxylic Acid Additive on Tridentate Titanium Catalyzed Enantioselective Hetero-Diels−Alder Reaction: Additive Acceleration and Nonlinear Effect. Chem. - Eur. J. 2002, 8, 5033−5042. (374) Yamaguchi, A.; Matsunaga, S.; Shibasaki, M. Direct Catalytic Asymmetric Mannich-Type Reactions of γ-Butenolides: Effectiveness of Brønsted Acid in Chiral Metal Catalysis. Org. Lett. 2008, 10, 2319− 2322. (375) Guan, X.-Y.; Yang, L.-P.; Hu, W. Cooperative Catalysis in Multicomponent Reactions: Highly Enantioselective Synthesis of γHydroxyketones with a Quaternary Carbon Stereocenter. Angew. Chem., Int. Ed. 2010, 49, 2190−2192. (376) Duan, Y.; Li, L.; Chen, M.-W.; Yu, C.-B.; Fan, H.-J.; Zhou, Y.G. Homogenous Pd-Catalyzed Asymmetric Hydrogenation of Unprotected Indoles: Scope and Mechanistic Studies. J. Am. Chem. Soc. 2014, 136, 7688−7700. (377) Marcoux, D.; Azzi, S.; Charette, A. B. TfNH2 as Achiral Hydrogen-Bond Donor Additive to Enhance the Selectivity of a Transition Metal Catalyzed Reaction. Highly Enantio- and Diastereoselective Rhodium-Catalyzed Cyclopropanation of Alkenes Using αCyano Diazoacetamide. J. Am. Chem. Soc. 2009, 131, 6970−6972. (378) Tao, Z.-L.; Zhang, W.-Q.; Chen, D.-F.; Adele, A.; Gong, L.-Z. Pd-Catalyzed Asymmetric Allylic Alkylation of Pyrazol-5-Ones with Allylic Alcohols: The Role of the Chiral Phosphoric Acid in C-O Bond Cleavage and Stereocontrol. J. Am. Chem. Soc. 2013, 135, 9255−9258. (379) Talbot, E. P. A.; Fernandes, T. D A.; McKenna, J. M.; Toste, F. D. Asymmetric Palladium-Catalyzed Directed Intermolecular Fluoroarylation of Styrenes. J. Am. Chem. Soc. 2014, 136, 4101−4104. (380) Meng, Q.; Zhu, L.; Zhang, Z. Highly Enantioselective Sequential Hydrogenation of Ethyl 2-Oxo-4-Arylbut-3-Enoate to Ethyl 2-Hydroxy-4-Arylbutyrate. J. Org. Chem. 2008, 73, 7209−7212. (381) Zhu, L.; Meng, Q.; Fan, W.; Xie, X.; Zhang, Z. Direct Asymmetric Hydrogenation of 2-Oxo-4-Arylbut-3-Enoic Acids. J. Org. Chem. 2010, 75, 6027−6030. (382) Kuwano, R.; Sato, K.; Kurokawa, T.; Karube, D.; Ito, Y. Catalytic Asymmetric Hydrogenation of Heteroaromatic Compounds, Indoles. J. Am. Chem. Soc. 2000, 122, 7614−7615. (383) Schrock, R. R.; Osborn, J. A. Catalytic Hydrogenation Using Cationic Rhodium Complexes. I. Evolution of the Catalytic System and the Hydrogenation of Olefins. J. Am. Chem. Soc. 1976, 98, 2134− 2143. (384) Fox, M. E.; Jackson, M.; Lennon, I. C.; Klosin, J.; Abboud, K. A. Bis-(2,5-diphenylphospholanes) with sp2 Carbon Linkers: Synthesis 4118


Chemical Reviews

Review

(403) Shu, C.; Leitner, A.; Hartwig, J. F. Enantioselective Allylation of Aromatic Amines after in Situ Generation of an Activated Cyclometalated Iridium Catalyst. Angew. Chem., Int. Ed. 2004, 43, 4797−4800. (404) Teichert, J. F.; Fañanás-Mastral, M.; Feringa, B. L. IridiumCatalyzed Asymmetric Intramolecular Allylic Amidation: Enantioselective Synthesis of Chiral Tetrahydroisoquinolines and Saturated Nitrogen Heterocycles. Angew. Chem., Int. Ed. 2011, 50, 688−691. (405) Xia, J.-B.; Liu, W.-B.; Wang, T.-M.; You, S.-L. Enantioselective Synthesis of 3-Azabicyclo[4.1.0]heptenes and 3-Azabicyclo[3.2.0]heptenes by Ir-Catalyzed Asymmetric Allylic Amination of N-Tosyl Propynylamine and Pt-Catalyzed Cycloisomerization. Chem. - Eur. J. 2010, 16, 6442−6446. (406) Kodama, K.; Sugawara, K.; Hirose, T. Synthesis of Chiral 1,3Diamines Derived from Cis-2-Benzamidocyclohexanecarboxylic Acid and Their Application in the Cu-Catalyzed Enantioselective Henry Reaction. Chem. - Eur. J. 2011, 17, 13584−13592. (407) Ishitani, H.; Ueno, M.; Kobayashi, S. Enantioselective Mannich-Type Reactions Using a Novel Chiral Zirconium Catalyst for the Synthesis of Optically Active β-Amino Acid Derivatives. J. Am. Chem. Soc. 2000, 122, 8180−8186. (408) Li, Z.; Yamamoto, H. Zirconium(IV)- and Hafnium(IV)Catalyzed Highly Enantioselective Epoxidation of Homoallylic and Bishomoallylic Alcohols. J. Am. Chem. Soc. 2010, 132, 7878−7880. (409) Yasui, Y.; Kamisaki, H.; Takemoto, Y. Enantioselective Synthesis of 3,3-Disubstituted Oxindoles through Pd-Catalyzed Cyanoamidation. Org. Lett. 2008, 10, 3303−3306. (410) Mashiko, T.; Kumagai, N.; Shibasaki, M. Managing Highly Coordinative Substrates in Asymmetric Catalysis: A Catalytic Asymmetric Amination with a Lanthanum-Based Ternary Catalyst. J. Am. Chem. Soc. 2009, 131, 14990−14999. (411) Liu, W.; Chen, D.; Zhu, X.-Z.; Wan, X.-L.; Hou, X.-L. Highly Diastereo- and Enantioselective Pd-Catalyzed Cyclopropanation of Acyclic Amides with Substituted Allyl Carbonates. J. Am. Chem. Soc. 2009, 131, 8734−8735. (412) Polet, D.; Rathgeb, X.; Falciola, C. A.; Langlois, J.-B.; El Hajjaji, S.; Alexakis, A. Enantioselective Iridium-Catalyzed Allylic Arylation. Chem. - Eur. J. 2009, 15, 1205−1216. (413) Evans, P. A.; Uraguchi, D. Regio- and Enantiospecific Rhodium-Catalyzed Arylation of Unsymmetrical Fluorinated Acyclic Allylic Carbonates: Inversion of Absolute Configuration. J. Am. Chem. Soc. 2003, 125, 7158−7159. (414) Duan, H.-F.; Xie, J.-H.; Qiao, X.-C.; Wang, L.-X.; Zhou, Q.-L. Enantioselective Rhodium-Catalyzed Addition of Arylboronic Acids to α-Ketoesters. Angew. Chem., Int. Ed. 2008, 47, 4351−4353. (415) Li, W.; Liu, X.; Hao, X.; Hu, X.; Chu, Y.; Cao, W.; Qin, S.; Hu, C.; Lin, L.; Feng, X. New Electrophilic Addition of α-Diazoesters with Ketones for Enantioselective C-N Bond Formation. J. Am. Chem. Soc. 2011, 133, 15268−15271. (416) Kurono, N.; Yoshikawa, T.; Yamasaki, M.; Ohkuma, T. Enantioselective Hydrocyanation of Aldehydes Catalyzed by [Li{Ru(phgly)2 (binap)}]X (X = Cl, Br). Org. Lett. 2011, 13, 1254−1257. (417) Kurono, N.; Arai, K.; Uemura, M.; Ohkuma, T. [Ru(phgly)2(binap)]/Li2CO3: A Highly Active, Robust, and Enantioselective Catalyst for the Cyanosilylation of Aldehydes. Angew. Chem., Int. Ed. 2008, 47, 6643−6646. (418) Kurono, N.; Nii, N.; Sakaguchi, Y.; Uemura, M.; Ohkuma, T. Asymmetric Hydrocyanation of α,β-Unsaturated Ketones into βCyano Ketones with the [Ru(phgly)2(binap)]/C6H5OLi Catalyst System. Angew. Chem., Int. Ed. 2011, 50, 5541−5544. (419) Suzuki, Y.; Yazaki, R.; Kumagai, N.; Shibasaki, M. Direct Catalytic Asymmetric Mannich-Type Reaction of Thioamides. Angew. Chem., Int. Ed. 2009, 48, 5026−5029. (420) Wang, C.; Yamamoto, H. Tungsten-Catalyzed Asymmetric Epoxidation of Allylic and Homoallylic Alcohols with Hydrogen Peroxide. J. Am. Chem. Soc. 2014, 136, 1222−1225. (421) Cherney, A. H.; Reisman, S. E. Nickel-Catalyzed Asymmetric Reductive Cross-Coupling between Vinyl and Benzyl Electrophiles. J. Am. Chem. Soc. 2014, 136, 14365−14368.

(422) Kakei, H.; Sone, T.; Sohtome, Y.; Matsunaga, S.; Shibasaki, M. Catalytic Asymmetric Cyclopropanation of Enones with Dimethyloxosulfonium Methylide Promoted by a La-Li3-(Biphenyldiolate)3 + NaI complex. J. Am. Chem. Soc. 2007, 129, 13410−13411. (423) Wooten, A. J.; Carroll, P. J.; Walsh, P. J. Impact of Na- and K-C π-interactions on the structure and binding of M 3 (sol)n(BINOLate)3Ln catalysts. Org. Lett. 2007, 9, 3359−3362. (424) Makino, K.; Hiroki, Y.; Hamada, Y. Dynamic Kinetic Resolution Catalyzed by Ir Axially Chiral Phosphine Catalyst: Asymmetric Synthesis of anti Aromatic β-Hydroxy-α-amino Acid Esters. J. Am. Chem. Soc. 2005, 127, 5784−5785. (425) Maaeda, T.; Makino, K.; Iwasaki, M.; Hamada. Diastereo- and Enantioselective Hydrogenation of α-Amino-β-Keto Ester Hydrochlorides Catalyzed by an Iridium Complex with MeO-BIPHEP and NaBArF: Catalytic Cycle and Five-Membered Chelation Mechanism of Asymmetric Hydrogenation. Y. Chem. - Eur. J. 2010, 16, 11954− 11962. (426) Li, J.; Cai, Y.; Chen, W.; Liu, X.; Lin, L.; Feng, X. Highly Enantioselective Fluorination of Unprotected 3-Substituted Oxindoles: One-Step Synthesis of BMS 204352 (MaxiPost). J. Org. Chem. 2012, 77, 9148−9155. (427) Toribatake, K.; Nishiyama, H. Asymmetric Diboration of Terminal Alkenes with a Rhodium Catalyst and Subsequent Oxidation: Enantioselective Synthesis of Optically Active 1,2-Diols. Angew. Chem., Int. Ed. 2013, 52, 11011−11015. (428) Hamada, T.; Manabe, K.; Kobayashi, S. Catalytic Asymmetric Mannich-type Reactions Activated by ZnF2 Chiral Diamine in Aqueous. Chem. - Eur. J. 2006, 12, 1205−1215. (429) Saito, B.; Katsuki, T. Synthesis of an OpticallyActive C1Symmetric Al(salalen) Complex and Its Application to the Catalytic Hydrophosphonylation of Aldehydes. Angew. Chem., Int. Ed. 2005, 44, 4600−4602. (430) Suyama, K.; Sakai, Y.; Matsumoto, K.; Saito, B.; Katsuki, T. Highly Enantioselective Hydrophosphonylation of Aldehydes: BaseEnhanced Aluminum-salalen Catalysis. Angew. Chem., Int. Ed. 2010, 49, 797−799. (431) Shang, G.; Liu, D.; Allen, S. E.; Yang, Q.; Zhang, X. Asymmetric Hydrogenation of α-Primary and Secondary Amino Ketones: Efficient Asymmetric Syntheses of (−)-Arbutamine and (−)-Denopamine. Chem. - Eur. J. 2007, 13, 7780−7784. (432) Wang, M.; Wang, Z.; Shi, Y.-H.; Shi, X.-X.; Fossey, J. S.; Deng, W.-P. An exo- and Enantioselective 1,3-Dipolar Cycloaddition of Azomethine Ylides with Alkylidene Malonates Catalyzed by a N,OLigand/Cu(OAc)2-Derived Chiral Complex. Angew. Chem., Int. Ed. 2011, 50, 4897−4900. (433) Stanley, L.i M.; Hartwig, J. F. Regio- and Enantioselective NAllylations of Imidazole, Benzimidazole, and Purine Heterocycles Catalyzed by Single-Component Metallacyclic Iridium Complexes. J. Am. Chem. Soc. 2009, 131, 8971−8983. (434) Sakuma, S.; Miyaura, N. Rhodium(I)-catalyzed Asymmetric 1,4-Addition of Arylboronic Acids to α,β-Unsaturated Amides. J. Org. Chem. 2001, 66, 8944−8946. (435) Trincado, M.; Ellman, J. A. Enantioselective Synthesis of α-Aryl Alkylamines by Rh-catalyzed Addition Reactions of Arylboronic Acids to Aliphatic Imines. Angew. Chem., Int. Ed. 2008, 47, 5623−5626. (436) Wang, Z.-Q.; Feng, C.-G.; Zhang, S.-S.; Xu, M.-H.; Lin, G.-Q. Rhodium-catalyzed Asymmetric Conjugate Addition of Organoboronic Acids to Nitroalkenes Using Chiral Bicyclo[3.3.0] Diene Ligands. Angew. Chem., Int. Ed. 2010, 49, 5780−5783. (437) Li, S.; Zhu, S.-F.; Xie, J.-H.; Song, S.; Zhang, C.-M.; Zhou, Q.L. Enantioselective Hydrogenation of α-Aryloxy and α-Alkoxy α,βUnsaturated Carboxylic Acids Catalyzed by Chiral Spiro Iridium/ Phosphino-Oxazoline Complexes. J. Am. Chem. Soc. 2010, 132, 1172− 1179. (438) Zhu, S.-F.; Yu, Y.-B.; Li, S.; Wang, L.-X.; Zhou, Q.-L. Enantioselective Hydrogenation of α-Substituted Acrylic Acids Catalyzed by Iridium Complexes with Chiral Spiro Aminophosphine Ligands. Angew. Chem., Int. Ed. 2012, 51, 8872−8875. 4119


Chemical Reviews

Review

metric Addition to Allenes. Angew. Chem., Int. Ed. 2015, 54, 7149− 7153. (458) Nemoto, T.; Matsumoto, T.; Masuda, T.; Hitomi, T.; Hatano, K.; Hamada, Y. P-Chirogenic Diaminophosphine Oxide: A New Class of Chiral Phosphorus Ligands for Asymmetric Catalysis. J. Am. Chem. Soc. 2004, 126, 3690−3691. (459) Wada, R.; Oisaki, K.; Kanai, M.; Shibasaki, M. Catalytic Enantioselective Allylboration of Ketones. J. Am. Chem. Soc. 2004, 126, 8910−8911. (460) Zhang, G.-W.; Meng, W.; Ma, H.; Nie, J.; Zhang, W.-Q.; Ma, J.A. Enantioselective Alkynylation of Trifluoromethyl Ketones: Pronounced Metal Fluoride Effects and Implications of Zinc-toTitanium Transmetallation. Angew. Chem., Int. Ed. 2011, 50, 3538− 3542. (461) Olivares-Romero, L. J.; Li, Z.; Yamamoto, H. Hf(IV)-Catalyzed Enantioselective Epoxidation of N-Alkenyl Sulfonamides and N-Tosyl Imines. J. Am. Chem. Soc. 2012, 134, 5440−5443. (462) Kondo, K.; Sodeoka, M.; Mori, M.; Shibasaki, M. Asymmetric Heck Reaction - Catalytic Asymmetric-Synthesis of Bicyclic Enones, Dienones and the Key Intermediate for Vernolepin. Synthesis 1993, 1993, 920−930. (463) Funabashi, K.; Saida, Y.; Kanai, M.; Arai, T.; Sasai, H.; Shibasaki, M. Catalytic Asymmetric Michael Addition of Nitromethane to Enones Controlled by (R)-LPB. Tetrahedron Lett. 1998, 39, 7557− 7558. (464) Kato, N.; Suzuki, M.; Kanai, M.; Shibasaki, M. General and Practical Catalytic Enantioselective Strecker Reaction of Ketoimines: Significant Improvement through Catalyst Tuning by Protic Additives. Tetrahedron Lett. 2004, 45, 3147−3151. (465) Mun, S.; Lee, J.-E.; Yun, J. Copper-Catalyzed β-Boration of α,β-Unsaturated Carbonyl Compounds: Rate Acceleration by Alcohol Additives. Org. Lett. 2006, 8, 4887−4889. (466) Lee, J.-E.; Kwon, J.; Yun, J. Copper-Catalyzed Addition of Diboron Reagents to α,β-Acetylenic Esters: Efficient Synthesis of βBoryl-α,β-Ethylenic Esters. Chem. Commun. 2008, 733−734. (467) Sim, H.-S.; Feng, X.; Yun. Copper-Catalyzed Enantioselective β-Boration of Acyclic Enones. Chem. - Eur. J. 2009, 15, 1939−1943. (468) Feng, X.; Yun. Conjugate Boration of β,β-Disubstituted Unsaturated Esters: Asymmetric Synthesis of Functionalized Chiral Tertiary Organoboronic Esters. Chem. - Eur. J. 2010, 16, 13609− 13612. (469) Hornillos, V.; Vila, C.; Otten, E.; Feringa, B. L. Catalytic Asymmetric Synthesis of Phosphine Boronates. Angew. Chem., Int. Ed. 2015, 54, 7867−7871. (470) Karimi, B.; Jafari, E.; Enders, D. Highly Efficient Catalytic Enantioselective Mannich Reaction of Malonates with N-tertButoxycarbonyl Imines by Using Yb(OTf)3/Pybox Catalysts at Room Temperature. Chem. - Eur. J. 2013, 19, 10142−10145. (471) Karimi, B.; Maleki, A. Catalytic Asymmetric Strecker Hydrocyanation of Imines Using Yb(OTf)3-Pybox Catalysts. Chem. Commun. 2009, 5180−5182. (472) Ishitani, H.; Yamashita, Y.; Shimizu, H.; Kobayashi, S. Highly anti-Selective Catalytic Asymmetric Aldol Reactions. J. Am. Chem. Soc. 2000, 122, 5403−5404. (473) Yamashita, Y.; Ishitani, H.; Shimizu, H.; Kobayashi, S. Highly anti-Selective Asymmetric Aldol Reactions Using Chiral Zirconium Catalysts. Improvement of Activities, Structure of the Novel Zirconium Complexes, and Effect of a Small Amount of Water for the Preparation of the Catalysts. J. Am. Chem. Soc. 2002, 124, 3292− 3302. (474) Seki, K.; Ueno, M.; Kobayashi, S. Storable, Powdered Chiral Zirconium Complex for Asymmetric Aldol and Hetero Diels−Alder Reactions. Org. Biomol. Chem. 2006, 5, 1347−1350. (475) Kobayashi, S.; Nagayama, S.; Busujima, T. Catalytic Asymmetric Mukaiyama Aldol Reactions in Aqueous Media. Tetrahedron 1999, 55, 8739−8746. (476) Yamashita, Y.; Kobayashi, S. Zirconium-Catalyzed Enantioselective [3 + 2] Cycloaddition of Hydrazones to Olefins Leading to

(439) Arai, T.; Mishiro, A.; Yokoyama, N.; Suzuki, K.; Sato, H. Chiral Bis(imidazolidine)pyridine-Cu(OTf)2: Catalytic Asymmetric endoSelective [3 + 2] Cycloaddition of Imino Esters with Nitroalkenes. J. Am. Chem. Soc. 2010, 132, 5338−5339. (440) Binder, J. T.; Cordier, C. J.; Fu, G. C. Catalytic Enantioselective Cross-Couplings of Secondary Alkyl Electrophiles with Secondary Alkylmetal Nucleophiles: Negishi Reactions of Racemic Benzylic Bromides with Achiral Alkylzinc Reagents. J. Am. Chem. Soc. 2012, 134, 17003−17006. (441) Amatore, M.; Lebœuf, D.; Malacria, M.; Gandon, V.; Aubert, C. Highly Enantioselective Rhodium-catalyzed [2 + 2 + 2] Cycloaddition of Diynes to Sulfonimines. J. Am. Chem. Soc. 2013, 135, 4576−4579. (442) Evans, P. A.; Lai, K. W.; Sawyer, J. R. Regio- and Enantioselective Intermolecular Rhodium-catalyzed [2 + 2 + 2] Carbocyclization Reactions of 1,6-Enynes with Methyl Arylpropiolates. J. Am. Chem. Soc. 2005, 127, 12466−12467. (443) Evans, P. A.; Sawyer, J. R.; Lai, K. W.; Huffman, J. C. Intermolecular Rhodium-catalyzed [2 + 2 + 2] Carbocyclization Reactions of 1,6-Enynes with Symmetrical and Unsymmetrical Alkynes. Chem. Commun. 2005, 3971−3973. (444) Kolb, A.; Zuo, W.; Siewert, J.; Harms, K.; von Zezschwitz, P. Improved Synthesis of Cyclic Tertiary Allylic Alcohols by Asymmetric 1,2-Addition of AlMe3 to Enones. Chem. - Eur. J. 2013, 19, 16366− 16373. (445) Huang, J.; Hsung, R. P. Chiral Lewis Acid-catalyzed Highly Enantioselective [4 + 3] Cycloaddition Reactions of NitrogenStabilized Oxyallyl Cations Derived from Allenamides. J. Am. Chem. Soc. 2005, 127, 50−51. (446) Evanno, L.; Ormala, J.; Pihko, P. M. A Highly Enantioselective Access to Tetrahydroisoquinoline and β-Carboline Alkaloids with Simple Noyori-Type Catalysts in Aqueous Media. Chem. - Eur. J. 2009, 15, 12963−12967. (447) Li, C.; Xiao, J. Asymmetric Hydrogenation of Cyclic Imines with an Ionic Cp*Rh(III) Catalyst. J. Am. Chem. Soc. 2008, 130, 13208−13209. (448) Phan, D. H. T.; Kim, B.; Dong, V. M. Phthalides by RhodiumCatalyzed Ketone Hydroacylation. J. Am. Chem. Soc. 2009, 131, 15608−15609. (449) Deng, Q.-H.; Bleith, T.; Wadepohl, H.; Gade, L. H. Enantioselective Iron-Catalyzed Azidation of β-Keto Esters and Oxindoles. J. Am. Chem. Soc. 2013, 135, 5356−5359. (450) Trost, B. M.; Xie, J.; Sieber, J. D. The Palladium Catalyzed Asymmetric Addition of Oxindoles and Allenes: An Atom-Economical Versatile Method for the Construction of Chiral Indole Alkaloids. J. Am. Chem. Soc. 2011, 133, 20611−20622. (451) Trost, B. M.; Simas, A. B. C.; Plietker, B.; Jäkel, C.; Xie, J. Enantioselective Palladium-Catalyzed Addition of 1,3-Dicarbonyl Compounds to an Allene Derivative. Chem. - Eur. J. 2005, 11, 7075−7082. (452) Wu, C.; Zhou, J. (Steve). Asymmetric Intermolecular Heck Reaction of Aryl Halides. J. Am. Chem. Soc. 2014, 136, 650−652. (453) Streuff, J.; Feurer, M.; Bichovski, P.; Frey, G.; Gellrich, U. Enantioselective Titanium(III)-Catalyzed Reductive Cyclization of Ketonitriles. Angew. Chem., Int. Ed. 2012, 51, 8661−8664. (454) Hamada, T.; Manabe, K.; Kobayashi, S. Enantio- and Diastereoselective, Stereospecific Mannich-type Reactions in Water. J. Am. Chem. Soc. 2004, 126, 7768−7769. (455) Wang, F.; Liu, H.; Cun, L.; Zhu, J.; Deng, J.; Jiang, Y. Asymmetric Transfer Hydrogenation of Ketones Catalyzed by Hydrophobic Metal-amido Complexes in Aqueous Micelles and Vesicles. J. Org. Chem. 2005, 70, 9424−9429. (456) Rhyoo, H. Y.; Park, H.-J.; Suh, W. H.; Chung, Y. K. Use of Surfactants in Water-Soluble Ruthenium(II) Complex-Catalyzed Asymmetric Hydrogen-Transfer Reduction of Aromatic Ketones. Tetrahedron Lett. 2002, 43, 269−272. (457) Haydl, A. M.; Xu, K.; Breit, B. Regio- and Enantioselective Synthesis of N-Substituted Pyrazoles by Rhodium-Catalyzed Asym4120


Chemical Reviews

Review

Optically Active Pyrazolidine, Pyrazoline, and 1,3-Diamine Derivatives. J. Am. Chem. Soc. 2004, 126, 11279−11282. (477) Wang, J.; Hu, X.; Jiang, J.; Gou, S.; Huang, X.; Liu, X.; Feng, X. Asymmetric Activation of Tropos 2,2 ′-Biphenol with Cinchonine Generates an Effective Catalyst for the Asymmetric Strecker Reaction of N-Tosyl-Protected Aldimines and Ketoimines. Angew. Chem., Int. Ed. 2007, 46, 8468−8470. (478) Wang, J.; Wang, W.; Li, W.; Hu, X.; Shen, K.; Tan, C.; Liu, X.; Feng, X. Asymmetric Cyanation of Aldehydes, Ketones, Aldimines, and Ketimines Catalyzed by a Versatile Catalyst Generated from Cinchona Alkaloid, Achiral Substituted 2,2′-Biphenol and Tetraisopropyl Titanate. Chem. - Eur. J. 2009, 15, 11642−11659. (479) Woo, S. K.; Geary, L. M.; Krische, M. J. Enantioselective Carbonyl Propargylation by Iridium-Catalyzed Transfer Hydrogenative Coupling of Alcohols and Propargyl Chlorides. Angew. Chem., Int. Ed. 2012, 51, 7830−7834. (480) Kubota, K.; Hayama, K.; Iwamoto, H.; Ito, H. Enantioselective Borylative Dearomatization of Indoles through Copper(I) Catalysis. Angew. Chem., Int. Ed. 2015, 54, 8809−8813. (481) Hatano, M.; Horibe, T.; Ishihara, K. Chiral Lithium(I) Binaphtholate Salts for the Enantioselective Direct Mannich-Type Reaction with a Change of Syn/Anti and Absolute Stereochemistry. J. Am. Chem. Soc. 2010, 132, 56−57. (482) Hatano, M.; Ikeno, T.; Miyamoto, T.; Ishihara, K. Chiral Lithium Binaphtholate Aqua Complex as a Highly Effective Asymmetric Catalyst for Cyanohydrin Synthesis. J. Am. Chem. Soc. 2005, 127, 10776−10777. (483) Hatano, M.; Ikeno, T.; Matsumura, T.; Torii, S.; Ishihara, K. Chiral Lithium Salts of Phosphoric Acids as Lewis Acid-Base Conjugate Catalysts for the Enantioselective Cyanosilylation of Ketones. Adv. Synth. Catal. 2008, 350, 1776−1780. (484) Trost, B. M.; Frederiksen, M. U. Palladium-Catalyzed Asymmetric Allylation of Prochiral Nucleophiles: Synthesis of 3Allyl-3-Aryl Oxindoles. Angew. Chem., Int. Ed. 2005, 44, 308−310. (485) Trost, B. M.; Czabaniuk, L. C. Palladium-Catalyzed Asymmetric Benzylation of 3-Aryl Oxindoles. J. Am. Chem. Soc. 2010, 132, 15534−15536. (486) Trost, B. M.; Czabaniuk, L. C. Palladium-Catalyzed Asymmetric Benzylation of Azlactones. Chem. - Eur. J. 2013, 19, 15210−15218. (487) Hughes, G.; Kimura, M.; Buchwald, S. L. Catalytic Enantioselective Conjugate Reduction of Lactones and Lactams. J. Am. Chem. Soc. 2003, 125, 11253−11258. (488) Rainka, M. P.; Aye, Y.; Buchwald, S. L. Copper-Catalyzed Asymmetric Conjugate Reduction as a Route to Novel βAzaheterocyclic Acid Derivatives. Proc. Natl. Acad. Sci. U. S. A. 2004, 101, 5821−5823. (489) Lipshutz, B. H.; Servesko, J. M.; Taft, B. R. Asymmetric 1,4Hydrosilylations of α,β-Unsaturated Esters. J. Am. Chem. Soc. 2004, 126, 8352−8353. (490) Sui, Y.-Z.; Zhang, X.-C.; Wu, J.-W.; Li, S.; Zhou, J.-N.; Li, M.; Fang, W.; Chan, A. S. C.; Wu, J. CuII-Catalyzed Asymmetric Hydrosilylation of Diaryl- and Aryl Heteroaryl Ketones: Application in the Enantioselective Synthesis of Orphenadrine and Neobenodine. Chem. - Eur. J. 2012, 18, 7486−7492. (491) Yun, J.; Buchwald, S. L. Titanocene-Catalyzed Asymmetric Ketone Hydrosilylation: The Effect of Catalyst Activation Protocol and Additives on the Reaction Rate and Enantioselectivity. J. Am. Chem. Soc. 1999, 121, 5640−5644. (492) Evans, D. A.; Rovis, T.; Kozlowski, M. C.; Downey, C. W.; Tedrow, J. S. Enantioselective Lewis Acid Catalyzed Michael Reactions of Alkylidene Malonates. Catalysis by C2-Symmetric Bis(oxazoline) Copper(II) Complexes in the Synthesis of Chiral, Differentiated Glutarate Esters. J. Am. Chem. Soc. 2000, 122, 9134−9142. (493) Evans, D. A.; Willis, M. C.; Johnston, J. N. Catalytic Enantioselective Michael Additions to Unsaturated Ester Derivatives Using Chiral Copper(II) Lewis Acid Complexes. Org. Lett. 1999, 1, 865−868.

(494) Evans, D. A.; Johnson, J. S.; Olhava, E. J. Enantioselective Synthesis of Dihydropyrans. Catalysis of Hetero Diels−Alder Reactions by Bis(oxazoline) Copper(II) Complexes. J. Am. Chem. Soc. 2000, 122, 1635−1649. (495) Evans, D. A.; Scheidt, K. A.; Johnston, J. N.; Willis, M. C. Enantioselective and Diastereoselective Mukaiyama-Michael Reactions Catalyzed by Bis(oxazoline) Copper(II) Complexes. J. Am. Chem. Soc. 2001, 123, 4480−4491. (496) Frings, M.; Atodiresei, I.; Wang, Y.; Runsink, J.; Raabe, G.; Bolm, C. Catalyzed Vinylogous Mukaiyama Aldol Reactions with Controlled Enantio- and Diastereoselectivities. Chem. - Eur. J. 2010, 16, 4577−4587. (497) Frings, M.; Atodiresei, I.; Runsink, J.; Raabe, G.; Bolm, C. Catalyzed Vinylogous Mukaiyama Aldol Reactions with Controlled Enantio- and Diastereoselectivities. Chem. - Eur. J. 2009, 15, 1566− 1569. (498) Li, J.; Huang, R.; Xing, Y.-K.; Qiu, G.; Tao, H.-Y.; Wang, C.-J. Catalytic Asymmetric Cascade Vinylogous Mukaiyama 1,6-Michael/ Michael Addition of 2-Silyloxyfurans with Azoalkenes: Direct Approach to Fused Butyrolactones. J. Am. Chem. Soc. 2015, 137, 10124−10127. (499) Arai, T.; Yokoyama, N. Tandem Catalytic Asymmetric Friedel−Crafts/Henry reaction: Control of Three Contiguous Acyclic Stereocenters. Angew. Chem., Int. Ed. 2008, 47, 4989−4992. (500) Cao, P.; Deng, C.; Zhou, Y.-Y.; Sun, X.-L.; Zheng, J.-C.; Xie, Z.; Tang, Y. Asymmetric Nazarov Reaction Catalyzed by Chiral Tris(oxazoline)/Copper(II). Angew. Chem., Int. Ed. 2010, 49, 4463− 4466. (501) Xu, X.; Hu, W.-H.; Doyle, M. P. Highly Enantioselective Catalytic Synthesis of Functionalized Chiral Diazoacetoacetates. Angew. Chem., Int. Ed. 2011, 50, 6392−6395. (502) Dahmen, S. Enantioselective Alkynylation of Aldehydes Catalyzed by [2.2] Paracyclophane-Based Ligands. Org. Lett. 2004, 6, 2113−2116. (503) Zhong, J.-C.; Hou, S.-C.; Bian, Q.-H.; Yin, M.-M.; Na, R.-S.; Zheng, B.; Li, Z.-Y.; Liu, S.-Z.; Wang, M. Highly Enantioselective Zinc/Amino Alcohol-Catalyzed Alkynylation of Aldehydes. Chem. Eur. J. 2009, 15, 3069−3071. (504) Wang, M.-C.; Zhang, Q.-J.; Zhao, W.-X.; Wang, X.-D.; Ding, X.; Jing, T.-T.; Song, M.-P. Evaluation of Enantiopure N(Ferrocenylmethyl)azetidin-2-l(diphenyl)methanol for Catalytic Asymmetric Addition of Organozinc Reagents to Aldehydes. J. Org. Chem. 2008, 73, 168−176. (505) Ito, J.-I.; Teshima, T.; Nishiyama, H. Enhancement of Enantioselectivity by Alcohol Additives in Asymmetric Hydrogenation with Bis(oxazolinyl)phenyl Ruthenium Catalysts. Chem. Commun. 2012, 48, 1105−1107. (506) Trost, B. M.; Malhotra, S.; Fried, B. A. Development of the Enantioselective Addition of Ethyl Diazoacetate to Aldehydes: Asymmetric Synthesis of 1,2-Diols. J. Am. Chem. Soc. 2009, 131, 1674−1675. (507) Trost, B. M.; Malhotra, S.; Koschker, P.; Ellerbrock, P. Development of the Enantioselective Addition of Ethyl Diazoacetate to Aldehydes: Asymmetric Synthesis of 1,2-Diols. J. Am. Chem. Soc. 2012, 134, 2075−2084. (508) Trost, B. M.; Malhotra, S.; Ellerbrock, P. Exploring the Unique Reactivity of Diazoesters: An Efficient Approach to Chiral β-Amino Acids. Org. Lett. 2013, 15, 440−443. (509) Yukawa, T.; Seelig, B.; Xu, Y.; Morimoto, H.; Matsunaga, S.; Berkessel, A.; Shibasaki, M. Catalytic Asymmetric Aza-Morita−Baylis− Hillman Reaction of Methyl Acrylate: Role of a Bifunctional La(O-iPr)3/Linked-BINOL Complex. J. Am. Chem. Soc. 2010, 132, 11988−11992. (510) Robiette, R.; Aggarwal, V. K.; Harvey, J. N. Mechanism of the Morita−Baylis−Hillman Reaction: A Computational Investigation. J. Am. Chem. Soc. 2007, 129, 15513−15525. (511) Kato, N.; Suzuki, M.; Kanai, M.; Shibasaki, M. General and Practical Catalytic Enantioselective Strecker Reaction of Ketoimines: 4121


Chemical Reviews

Review

Significant Improvement through Catalyst Tuning by Protic Additives. Tetrahedron Lett. 2004, 45, 3147−3151. (512) Kato, N.; Suzuki, M.; Kanai, M.; Shibasaki, M. Catalytic Enantioselective Strecker Reaction of Ketoimines Using Catalytic Amount of TMSCN and Stoichiometric Amount of HCN. Tetrahedron Lett. 2004, 45, 3153−3155. (513) Masumoto, S.; Usuda, H.; Suzuki, M.; Kanai, M.; Shibasaki, M. Catalytic Enantioselective Strecker Reaction of Ketoimines. J. Am. Chem. Soc. 2003, 125, 5634−5635. (514) Tanaka, Y.; Kanai, M.; Shibasaki, M. A Catalytic Enantioselective Conjugate Addition of Cyanide to Enones. J. Am. Chem. Soc. 2008, 130, 6072−6073. (515) Mita, T.; Sasaki, K.; Kanai, M.; Shibasaki, M. Catalytic Enantioselective Conjugate Addition of Cyanide to α,β-Unsaturated N-Acylpyrroles. J. Am. Chem. Soc. 2005, 127, 514−515. (516) Shi, S.-L.; Kanai, M.; Shibasaki, M. Asymmetric Synthesis of Dihydropyranones from Ynones by Sequential Copper(I)-Catalyzed Direct Aldol and Silver(I)-Catalyzed Oxy-Michael Reactions. Angew. Chem., Int. Ed. 2012, 51, 3932−3935. (517) Handa, S.; Gnanadesikan, V.; Matsunaga, S.; Shibasaki, M. Heterobimetallic Transition Metal/Rare Earth Metal Bifunctional Catalysis: A Cu/Sm/Schiff Base Complex for Syn-Selective Catalytic Asymmetric Nitro-Mannich Reaction. J. Am. Chem. Soc. 2010, 132, 4925−4934. (518) Ohmura, T.; Awano, T.; Suginome, M. Stereospecific SuzukiMiyaura Coupling of Chiral α-(Acylamino)benzylboronic Esters with Inversion of Configuration. J. Am. Chem. Soc. 2010, 132, 13191− 13193. (519) Awano, T.; Ohmura, T.; Suginome, M. Inversion or Retention? Effects of Acidic Additives on the Stereochemical Course in Enantiospecific Suzuki-Miyaura Coupling of α-(Acetylamino)benzylboronic Esters. J. Am. Chem. Soc. 2011, 133, 20738−20741. (520) Hoen, R.; Boogers, J. A. F.; Bernsmann, H.; Minnaard, A. J.; Meetsma, A.; Tiemersma-Wegman, T. D.; de Vries, A. H. M.; de Vries, J. G.; Feringa, B. L. Achiral Ligands Dramatically Enhance Rate and Enantioselectivity in the Rh/Phosphoramidite-Catalyzed Hydrogenation of α,β-Disubstituted Unsaturated Acids. Angew. Chem., Int. Ed. 2005, 44, 4209−4212. (521) Li, Y.; Dong, K.; Wang, Z.; Ding, K. Rhodium(I)-Catalyzed Enantioselective Hydrogenation of Substituted Acrylic Acids with Sterically Similar β,β-Diaryls. Angew. Chem., Int. Ed. 2013, 52, 6748− 6752. (522) Dong, K.; Li, Y.; Wang, Z.; Ding, K. Catalytic Asymmetric Hydrogenation of α-CF3- or β-CF3-Substituted Acrylic Acids Using Rhodium(I) Complexes with a Combination of Chiral and Achiral Ligands. Angew. Chem., Int. Ed. 2013, 52, 14191−14195. (523) Hojo, D.; Noguchi, K.; Tanaka, K. Synthesis of Chiral Tetrasubstituted Alkenes by an Asymmetric Cascade Reaction Catalyzed Cooperatively by Cationic Rhodium(I) and Silver(I) Complexes. Angew. Chem., Int. Ed. 2009, 48, 8129−8132. (524) Yamagiwa, N.; Tian, J.; Matsunaga, S.; Shibasaki, M. Catalytic Asymmetric Cyano-Ethoxycarbonylation Reaction of Aldehydes Using a YLi3Tris(binaphthoxide) (YLB) Complex: Mechanism and Roles of Achiral Additives. J. Am. Chem. Soc. 2005, 127, 3413−3422. (525) Yamasaki, S.; Kanai, M.; Shibasaki, M. Novel Multiaction of Zr Catalyst: One-Pot Synthesis of β-Cyanohydrins from Olefins. J. Am. Chem. Soc. 2001, 123, 1256−1257. (526) Sone, T.; Yamaguchi, A.; Matsunaga, S.; Shibasaki, M. Catalytic Asymmetric Synthesis of 2,2-Disubstituted Terminal Epoxides via Dimethyloxosulfonium Methylide Addition to Ketones. J. Am. Chem. Soc. 2008, 130, 10078−10079. (527) Hara, K.; Park, S.-Y.; Yamagiwa, N.; Matsunaga, S.; Shibasaki, M. Catalytic Asymmetric Epoxidation of α,β-Unsaturated Phosphane Oxides with a Y(O-iPr)3/Biphenyldiol Complex. Chem. - Asian J. 2008, 3, 1500−1504. (528) Kino, R.; Daikai, K.; Kawanami, T.; Furuno, H.; Inanaga, J. Remarkable Effect of Tris(4-fluorophenyl)phosphine Oxide on the Stabilization of Chiral Lanthanum Complex Catalysts. A New and

Practical Protocol for the Highly Enantioselective Epoxidation of Conjugated Enones. Org. Biomol. Chem. 2004, 2, 1822−1824. (529) Yazaki, R.; Kumagai, N.; Shibasaki, M. Direct Catalytic Asymmetric Addition of Allyl Cyanide to Ketones via Soft Lewis Acid/ Hard Brønsted Base/Hard Lewis Base Catalysis. J. Am. Chem. Soc. 2010, 132, 5522−5531. (530) Iwata, M.; Yazaki, R.; Chen, I.-H.; Sureshkumar, D.; Kumagai, N.; Shibasaki, M. Direct Catalytic Enantio- and Diastereoselective Aldol Reaction of Thioamides. J. Am. Chem. Soc. 2011, 133, 5554− 5560. (531) Wieland, L. C.; Deng, H.; Snapper, M. L.; Hoveyda, A. H. AlCatalyzed Enantioselective Alkylation of α-Ketoesters by Dialkylzinc Reagents. Enhancement of Enantioselectivity and Reactivity by an Achiral Lewis Base Additive. J. Am. Chem. Soc. 2005, 127, 15453− 15456. (532) Friel, D. K.; Snapper, M. L.; Hoveyda, A. H. AluminumCatalyzed Asymmetric Alkylations of Pyridyl-Substituted Alkynyl Ketones with Dialkylzinc Reagents. J. Am. Chem. Soc. 2008, 130, 9942−9951. (533) Zhao, D.; Wang, L.; Yang, D.; Zhang, Y.; Wang, R. Highly Diastereo- and Enantioselective Synthesis of α-Alkyl Norstatine Derivatives: Catalytic Asymmetric Mannich Reactions of 5H-Oxazol4-ones. Angew. Chem., Int. Ed. 2012, 51, 7523−7527. (534) Xiao, D.; Zhang, X. Highly Enantioselective Hydrogenation of Acyclic Imines Catalyzed by Ir-f-Binaphane Complexes. Angew. Chem., Int. Ed. 2001, 40, 3425−3428. (535) Chi, Y.; Zhou, Y.-G.; Zhang, X. Highly Enantioselective Reductive Amination of Simple Aryl Ketones Catalyzed by Ir-fBinaphane in the Presence of Titanium(IV) Isopropoxide and Iodine. J. Org. Chem. 2003, 68, 4120−4122. (536) Wang, W.-B.; Lu, S.-M.; Yang, P.-Y.; Han, X.-W.; Zhou, Y.-G. Highly Enantioselective Iridium-Catalyzed Hydrogenation of Heteroaromatic Compounds, Quinolones. J. Am. Chem. Soc. 2003, 125, 10536−10537. (537) Wang, D.-W.; Wang, X.-B.; Wang, D.-S.; Lu, S.-M.; Zhou, Y.G.; Li, Y.-X. Highly Enantioselective Iridium-Catalyzed Hydrogenation of 2-Benzylquinolines and 2-Functionalized and 2,3-Disubstituted Quinolines. J. Org. Chem. 2009, 74, 2780−2787. (538) Shi, L.; Ye, Z.-S.; Cao, L.-L.; Guo, R.-N.; Hu, Y.; Zhou, Y.-G. Enantioselective Iridium-Catalyzed Hydrogenation of 3,4-Disubstituted Isoquinolines. Angew. Chem., Int. Ed. 2012, 51, 8286−8289. (539) Tang, W.; Xu, L.; Fan, Q.-H.; Wang, J.; Fan, B.; Zhou, Z.; Lam, K.-H.; Chan, A. S. C. Asymmetric Hydrogenation of Quinoxalines with Diphosphinite Ligands: A Practical Synthesis of Enantioenriched, Substituted Tetrahydroquinoxalines. Angew. Chem., Int. Ed. 2009, 48, 9135−9138. (540) Hou, G.-H.; Xie, J.-H.; Wang, L.-X.; Zhou, Q.-L. Highly Efficient Rh(I)-Catalyzed Asymmetric Hydrogenation of Enamines Using Monodente Spiro Phosphonite Ligands. J. Am. Chem. Soc. 2006, 128, 11774−11775. (541) Hou, G.-H.; Xie, J.-H.; Yan, P.-C.; Zhou, Q.-L. IridiumCatalyzed Asymmetric Hydrogenation of Cyclic Enamines. J. Am. Chem. Soc. 2009, 131, 1366−1367. (542) Xie, M.; Liu, X.; Zhu, Y.; Zhao, X.; Xia, Y.; Lin, L.; Feng, X. Asymmetric Synthesis of Tetrahydroquinolines with Quaternary Stereocenters through the Povarov Reaction. Chem. - Eur. J. 2011, 17, 13800−13805. (543) Lutz, F.; Igarashi, T.; Kawasaki, T.; Soai, K. Small Amounts of Achiral β-Amino Alcohols Reverse the Enantioselectivity of Chiral Catalysts in Cooperative Asymmetric Autocatalysis. J. Am. Chem. Soc. 2005, 127, 12206−12207. (544) Lutz, F.; Igarashi, T.; Kinoshita, T.; Asahina, M.; Tsukiyama, K.; Kawasaki, T.; Soai, K. Mechanistic Insights in the Reversal of Enantioselectivity of Chiral Catalysts by Achiral Catalysts in Asymmetric Autocatalysis. J. Am. Chem. Soc. 2008, 130, 2956−2958. (545) Lavabre, D.; Micheau, J.-C.; Islas, J. R.; Buhse, T. Enantioselectivity Reversal by Achiral Additives in the Soai Reaction: A Kinetic Understanding. J. Phys. Chem. A 2007, 111, 281−286. 4122


Chemical Reviews

Review

(546) Shibata, T.; Tarumi, H.; Kawasaki, T.; Soai, K. Reversal in Enantioselectivity Induced by Achiral Alcohols in Asymmetric Autocatalysis in the Presence of a Chiral Diol as a Chiral Initiator. Tetrahedron: Asymmetry 2012, 23, 1023−1027. (547) Rudolph, J.; Hermanns, N.; Bolm, C. The MPEG effect: Improving Asymmetric Processes by Simple Additives. J. Org. Chem. 2004, 69, 3997−4000. (548) Funabashi, K.; Jachmann, M.; Kanai, M.; Shibasaki, M. Multicenter Strategy for the Development of Catalytic Enantioselective Nucleophilic Alkylation of Ketones: Me2Zn Addition to αKetoesters. Angew. Chem., Int. Ed. 2003, 42, 5489−5492. (549) Wu, H.-L.; Wu, P.-Y.; Shen, Y.-Y.; Uang, B.-J. Asymmetric Addition of Dimethylzinc to α-Ketoesters Catalyzed by (−)-MITH. J. Org. Chem. 2008, 73, 6445−6447. (550) Watson, M. P.; Jacobsen, E. N. Asymmetric Intramolecular Arylcyanation of Unactivated Olefins via C-CN Bond Activation. J. Am. Chem. Soc. 2008, 130, 12594−12595. (551) Brunkan, N. M.; Brestensky, D. M.; Jones, W. D. Kinetics, Thermodynamics, and Effect of BPh3 on Competitive C-C and C-H bond Activation Reactions in the Interconversion of Allyl Cyanide by [Ni(dippe)]. J. Am. Chem. Soc. 2004, 126, 3627−3641. (552) Hansen, K. B.; Rosner, T.; Kubryk, M.; Dormer, P. G.; Armstrong, J. D., III Detection and Elimination of Product Inhibition from the Asymmetric Catalytic Hydrogenation of Enamines. Org. Lett. 2005, 7, 4935−4938. (553) Chen, F.; Ding, Z.; He, Y.; Qin, J.; Wang, T.; Fan, Q.-H. Asymmetric Hydrogenation of N-Alkyl and N-Aryl Ketimines Using Chiral Cationic Ru(diamine) Complexes as Catalysts: The Counteranion and Solvent Effects, and Substrate Scope. Tetrahedron 2012, 68, 5248−5257. (554) Chen, F.; Wang, T.; He, Y.; Ding, Z.; Li, Z.; Xu, L.; Fan, Q.-H. Asymmetric Hydrogenation of N-Alkyl Ketimines with PhosphineFree, Chiral, Cationic Ru-MsDPEN Catalysts. Chem. - Eur. J. 2011, 17, 1109−1113. (555) Chen, F.; Ding, Z.; Qin, J.; Wang, T.; He, Y.; Fan, Q.-H. Highly Effective Asymmetric Hydrogenation of Cyclic N-Alkyl Imines with Chiral Cationic Ru-MsDPEN Catalysts. Org. Lett. 2011, 13, 4348−4351. (556) Usanov, D. L.; Yamamoto, H. Asymmetric Nozaki-Hiyama Propargylation of Aldehydes: Enhancement of Enantioselectivity by Cobalt Co-Catalysis. Angew. Chem., Int. Ed. 2010, 49, 8169−8172. (557) Chen, M.; Hartwig, J. F. Iridium-Catalyzed Enantioselective Allylic Substitution of Unstabilized Enolates Derived from α,βUnsaturated Ketone. Angew. Chem., Int. Ed. 2014, 53, 8691−8695. (558) Chen, M.; Hartwig, J. F. Iridium-Catalyzed Regio- and Enantioselective Allylic Substitution of Silyl Dienolates Derived from Dioxinones. Angew. Chem., Int. Ed. 2014, 53, 12172−12176. (559) Chen, M.; Hartwig, J. F. Iridium-Catalyzed Enantioselective Allylic Substitution of Enol Silanes from Vinylogous Esters and Amides. J. Am. Chem. Soc. 2015, 137, 13972. (560) Turnbull, B. W. H.; Evans, P. A. Enantioselective RhodiumCatalyzed Allylic Substitution with a Nitrile Anion: Construction of Acyclic Quaternary Carbon Stereogenic Centers. J. Am. Chem. Soc. 2015, 137, 6156−6159. (561) Nelson, H. M.; Williams, B. D.; Miró, J.; Toste, F. D. Enantioselective 1,1-Arylborylation of Alkenes: Merging Chiral Anion Phase Transfer with Pd Catalysis. J. Am. Chem. Soc. 2015, 137, 3213− 3216. (562) Davies, H. M. L.; Venkataramani, C. Dirhodium Tetraprolinate-Catalyzed Asymmetric Cycloproplanations with High Turnover Numbers. Org. Lett. 2003, 5, 1403−1406. (563) Nelson, T. D.; Song, Z. J.; Thompson, A. S.; Zhao, M.; DeMarco, A.; Reamer, R. A.; Huntington, M. F.; Grabowski, E. J. J.; Reider, P. J. Rhodium-Carbenoid-Mediated Intermolecular O-H Insertion Reactions: a Dramatic Additive Effect. Application in the Synthesis of an Ascomycin Derivative. Tetrahedron Lett. 2000, 41, 1877−1881. (564) Wynne, D. C.; Olmstead, M. M.; Jessop, P. G. Supercritical and Liquid Solvent Effects on the Enantioselectivity of Asymmetric

Cyclopropanation with Tetrakis[1-[(4-tert-butylphenyl)-sulfonyl](2S)-pyrrolidinecarboxylate]dirhodium(II). J. Am. Chem. Soc. 2000, 122, 7638−7647. (565) Li, K.; Alexakis, A. Asymmetric Conjugate Addition to α-Halo Enones: Dramatic Effect of Styrene on the Enantioselectivity. Angew. Chem., Int. Ed. 2006, 45, 7600−7603. (566) Evans, D. A.; Tedrow, J. S.; Shaw, J. T.; Downey, C. W. Diastereoselective Magnesium Halide-Catalyzed Anti-Aldol Reactions of Chiral N-Acyloxazolidinones. J. Am. Chem. Soc. 2002, 124, 392− 393. (567) Miranda, P. O.; Carballo, R. M.; Martín, V. S.; Padrón, J. I. A New Catalytic Prins Cyclization Leading to Oxa- and Azacycles. Org. Lett. 2009, 11, 357−360. (568) Downey, C. W.; Mahoney, B. D.; Lipari, V. R. Trimethylsilyl Trifluoromethanesulfonate-Accelerated Addition of Catalytically Generated Zinc Acetylides to Aldehydes. J. Org. Chem. 2009, 74, 2904− 2906. (569) Saito, T.; Nishimoto, Y.; Yasuda, M.; Baba, A. Direct Coupling Reaction between Alcohols and Silyl Compounds: Enhancement of Lewis Acidity of Me3SiBr using InCl3. J. Org. Chem. 2006, 71, 8516− 8522. (570) Lee, P. H.; Seomoon, D.; Kim, S.; Nagaiah, K.; Damle, S. V.; Lee, K. Efficient Addition of Allylsilanes to α,β-Enones Using Catalytic Indium and Trimethylsilyl Chloride. Synthesis 2003, 2189−2193. (571) Hanhan, N. V.; Ball-Jones, N. R.; Tran, N. T.; Franz, A. K. Catalytic Asymmetric [3 + 2] Annulation of Allylsilanes with Isatins: Synthesis of Spirooxindoles. Angew. Chem., Int. Ed. 2012, 51, 989−992. (572) Bao, H.; Zhou, J.; Wang, Z.; Guo, Y.; You, T.; Ding, K. Insight into the Mechanism of the Asymmetric Ring-Opening Aminolysis of 4,4-Dimethyl-3,5,8-Trioxabicyclo[5.1.0]octane Catalyzed by Titanium/BINOLate/Water System: Evidence for the Ti(BINOLate)2Bearing Active Catalyst Entities and the Role of Water. J. Am. Chem. Soc. 2008, 130, 10116−10127. (573) Pescitelli, G.; Di Bari, L.; Salvadori, P. Effect of Water on BINOL/Ti(OiPr)4 Solution Mixtures: The Nature of a Catalytic Precursor of Enantioselective Sulfoxidation. J. Organomet. Chem. 2006, 691, 2311−2318. (574) Komatsu, N.; Hashizume, M.; Sugita, T.; Uemura, S. Catalytic Asymmetric Oxidation of Sulfides to Sulfoxides with tert-Butyl Hydroperoxide Using Binaphthol as a Chiral Auxiliary. J. Org. Chem. 1993, 58, 4529−4533. (575) Komatsu, N.; Hashizume, M.; Sugita, T.; Uemura, S. Kinetic Resolution of Sulfoxides Catalyzed by Chiral Titanium-Binaphthol Complex. J. Org. Chem. 1993, 58, 7624−7626. (576) Schlüter, J.; Blazejak, M.; Boeck, F.; Hintermann, L. Asymmetric Hydroalkoxylation of Non-Activated Alkenes: TitaniumCatalyzed Cycloisomerization of Allylphenols at High Temperatures. Angew. Chem., Int. Ed. 2015, 54, 4014−4017. (577) Li, Q.; Fu, C.; Ma, S. Catalytic Asymmetric Allenylation of Malonates with the Generation of Central Chirality. Angew. Chem., Int. Ed. 2012, 51, 11783−11786.

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