Letter Cite This: Org. Lett. XXXX, XXX, XXX−XXX
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Remote 1,5-Stereoselectivity Control by an N‑Ligand Switch in the Pd(0)/InI-Promoted Reactions of 4‑Ethynyl-β-lactams with Aldehydes Sylwia Domin,† Jacek Kędzierski, and Bartosz K. Zambroń* Institute of Organic Chemistry, Polish Academy of Sciences, Kasprzaka 44/52, 01-224 Warsaw, Poland Org. Lett. Downloaded from pubs.acs.org by UNIV AUTONOMA DE COAHUILA on 05/16/19. For personal use only.
S Supporting Information *
ABSTRACT: Configurationally stable ε-amido-propargylindiums, generated in situ from N-Ts-4-ethynylazetidin-2-ones in the presence of InI, catalytic amounts of Pd(PPh3)4, and Nmethylimidazole or pyridine ligand react with unusual regioselectivity with aromatic and aliphatic aldehydes to afford 2,6-syn- or 2,6-anti-allenediols with excellent central-to-axial chirality transfer and useful levels of acyclic remote 1,5stereocontrol.
D
their application deal with stereoselective ring-opening reactions upon treatment with various types of nucleophiles.5 In contrast, the reactions of β-lactams with electrophiles are rare.4,6 Initially, the formation of propargylindium from readily accessible racemic N-Ts-4-ethynylazetidin-2-one 1 and its subsequent addition to benzaldehyde under our two previously reported conditions was attempted.4a,c The application of 2 equiv of InI and 5 mol % of Pd(PPh3)4 in a 3:1 THF/HMPA7 mixture at 25 °C gave exclusively 2,5-syn-allenediol 2 in high 79% total yield and with excellent central-to-axial chirality transfer. However, an inseparable mixture of two C6-epimers 2a and 2b (43:57 d.r.) was obtained (Table 1, entry 1). Carrying out the reaction in the presence of 3 equiv of InI and 5 mol % of Pd(PPh3)4 in a 9:1 THF/EtOH mixture with the addition of 2 equiv of N-methylimidazole (N-MI) ligand, in turn, afforded product 2 in low 34% yield but with significantly higher (76:24 d.r.) 2,6-anti-selectivity (Table 1, entry 2). Consequently, in the next experiment β-lactam 1 was subjected to the reaction with benzaldehyde in a 9:1 THF/HMPA mixture with addition of 2 equiv of the N-MI. As a result, the product 2 was obtained in an acceptable 60% yield and with only slightly reduced (73:27 d.r.) 2,6-anti-selectivity (Table 1, entry 3). Further experiments using modified THF/HMPA ratio mixtures and attempts of replacing THF and/or toxic HMPA7 with other polar cosolvents (DMPU, DMI, DMF, NMP, and DMSO) failed since, in all cases, a noticeable drop in yield and/or stereoselectivity was observed. On the other hand, replacing N-MI with other amines (NEt3, DIPEA, quinuclidine, pyridine, 2,6-lutidine, quinoline, isoquinoline, Nmethylmorpholine) led to interesting results. While N-MI proved to be superior to other N-ligands examined for the synthesis of 2,5-syn-2,6-anti-epimer 2a, the application of 2
ue to high reactivity and unique properties resulting from the presence of two cumulated CC double bonds, axially chiral allenes constitute frequently used intermediates for the stereoselective synthesis of a variety of organic compounds.1 Moreover, the allene substructure is found within numerous natural products, often exhibiting valuable pharmacological activities.2 Thus, developing the methodology for new stereoselective entries into these interesting compounds is of high importance. The addition of nontoxic, watertolerant, and configurationally stable allenyl/propargylindiums, readily available from a number of propargyl alcohol derivatives, to carbonyl compounds constitutes a potentially useful method for the synthesis of functionalized chiral allenes.3 However, due to the occurrence of an equilibrium between propargyl and allenyl isomers, regioselectivity control in the subsequent addition step remains a challenging task. Recently, we have demonstrated that the addition of cyclic 4vinyl-β-lactam-derived ε-amido-allylindiums to aldehydes proceeds with atypical high α-regioselectivity to give the usually unfavorable linear homoallylic alcohols.4 The notion that the use of related 4-ethynyl-β-lactams in the analogous process might lead to a variety of structurally diverse axially chiral allenes led us to an examination of this potentially useful transformation. As a result, a new method for the stereoselective synthesis of highly functionalized axially chiral 2,6allenediols from readily available 4-ethynyl-azetidin-2-ones has been developed. It is noteworthy that the presented reaction constitutes a unique example of the addition of terminal secondary propargylindium to carbonyl compounds proceeding at the terminal position to give exclusively the allene products.3 In comparison, analogous reactions of structurally related 2-ethynylaziridines under similar conditions afforded exclusively 2-ethynyl-1,3-amino alcohols, typical propargylation products.3c,d Although chiral β-lactams are widely used intermediates for the asymmetric synthesis of diverse classes of organic compounds, the vast majority of reports concerning © XXXX American Chemical Society
Received: March 12, 2019
A
DOI: 10.1021/acs.orglett.9b00891 Org. Lett. XXXX, XXX, XXX−XXX
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Organic Letters
Table 2. Pd(PPh3)4/InI-Mediated Addition of β-Lactams 1 and (+)-1 to Aromatic and Aliphatic Aldehydes
Table 1. Optimization of the Reaction Conditions
entry 1 2 3 4 5 6
solvent THF/HMPA (3:1) THF/EtOH (9:1) THF/HMPA (9:1) THF/HMPA (9:1) THF/EtOH (9:1) THF/EtOH (9:1)
c
N-ligand
yield [%]a; (2a:2b)b
− N-MId N-MId PYe − PYe
79 (43:57) 34 (76:24) 60 (73:27) 53 (19:81) traces traces
a Isolated yields. bAssayed by 1H NMR integration. c2 equiv of InI were used. dN-Methylimidazole. ePyridine.
equiv of pyridine (PY) gave allenediol 2 in somewhat lower 53% yield, but with altered C6-hydroxy group configuration. In this case, 2,5-syn-2,6-syn-epimer 2b was formed as the major product with 81:19 d.r., resulting in significant reaction scope expansion (Table 1, entry 4). Control experiments conducted in a 9:1 THF/EtOH mixture, with PY or without N-ligand, confirmed that THF/HMPA is optimal since a complex mixture of products with only trace amounts of the desired allenes was obtained in these cases (Table 1, entries 5 and 6). It is noteworthy that although the beneficial effect of the Nligand additive on the related allylation rates and yields has been seldom reported,4c to the best of our knowledge the possibility of stereocontrol, including remote 1,5-asymmetric induction, in the allylation and propargylation/allenylation reactions with organoindiums by a ligand switch has not been reported to date. Next, a variety of aromatic and aliphatic aldehydes were subjected to the reaction with β-lactam 1 under optimized conditions using N-MI or PY ligands as additives. All of the reactions involving aromatic aldehydes, including furfural, afforded the expected 2,5-syn-allenediols 2−5 in moderate 45− 60% yields and with comparable 2,6-anti or 2,6-syn-selectivity depending on which N-ligand was applied (Table 2, entries 1− 5). Also reactions with aliphatic aldehydes, including 4hydroxybutyric aldehyde containing an unprotected hydroxyl group and sterically hindered pivalaldehyde, proceeded effectively, delivering the corresponding products in 46−61% yield (Table 2, entries 6−10). Although in these examples less efficient 1,5-stereocontrol was usually observed, the significant effect of both ligands on the remote asymmetric induction was clear. In the case of reactions with pivalaldehyde (Table 2, entry 9), 8−9% of two other C5-epimers of allenediol 8 were detected, indicating partial epimerization of the propargylindium intermediate, most likely due to the reduced addition rate caused by severe steric hindrance of the t-Bu substituent. Importantly, when enantioenriched N-Ts-4-ethynylazetidin-2one (+)-1 (>99% ee)8 was combined with benzaldehyde or isobutyric aldehyde under both conditions, no racemization occurred and the expected enantioenriched allenediols (−)-2a, (+)-2b and (−)-7a, (−)-7b were obtained as virtually optically pure compounds (>98% ee).8 These examples demonstrate that the developed method can be applied in asymmetric
a Isolated yields. bAssayed by 1HNMR integration. cβ-lactam (+)-1 (>99% ee)8 was used. d>98% ee.8 eContaining 8% of two C5-epimers (75:25 d.r.) according to 1HNMR. fContaining 9% of two C5-epimers (54:46 d.r.) according to 1HNMR.
synthesis, since a variety of β-lactams are readily available in both enantiomeric forms in excellent optical purity.9 In order to determine the effect of β-lactam chirality, trans-4ethynylazetidin-2-one 10 was subjected to the reaction with benzaldehyde under optimized reaction conditions (Scheme 1). As a result, 2,5-anti-allenediol 11 with altered axial Scheme 1. Pd(PPh3)4/InI-Mediated Addition of trans-βLactam 10 to Benzaldehyde
Isolated yield. b37% of β-lactam 10 was recovered. cAssayed by 1H NMR integration. d30% of β-lactam 10 was recovered. a
configuration, as compared to cis-β-lactam 1-derived 2,5-synisomers 2a and 2b, was obtained in 40% and 45% yield, respectively. This shows that configurationally stable ε-amidopropargylindiums are generated in a stereospecific manner and do not equilibrate under either reaction conditions.10 Although this doubles the number of potentially available axially chiral allenes from differently configured 4-ethynyl-β-lactams we could not achieve the diastereoselective synthesis of any C6B
DOI: 10.1021/acs.orglett.9b00891 Org. Lett. XXXX, XXX, XXX−XXX
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diasteromers of allenediols may be potentially produced.11 In the first case, the stabilization of ts-1 by N-MI ligand and the opposite effect of PY results in the possibility that compound 2a or 2b can be formed in excess, depending on which Nligand is applied. However, the exact nature of this effect is not clear. In the case of reactions of cis-ε-amido-propargylindium IIb derived from trans-β-lactam 10, the addition occurs via both transition states, regardless of which N-ligand is involved, affording the corresponding 2,5-anti-allenediols 11 as equimolar mixtures of C6-epimers 11a and 11b in both cases. In order to gain insight into the effect of the azetidin-2-one ring and ethynyl substitution, a number of modified cissubstituted β-lactams were subjected to the reaction with benzaldehyde under optimized conditions (Scheme 3).
epimer of compound 11 in this case, since under both conditions equimolar mixtures of 11a and 11b were formed. Even then, the method under development can be applied for the synthetic plans where the C6 configuration in the product is not relevant. A plausible reaction pathway of the above transformations, based on the observed regio- and stereoselectivity, is depicted in Scheme 2. In both cases, the initial step consists of Scheme 2. Plausible Reaction Pathway
Scheme 3. Pd(PPh3)4/InI-Mediated Additions of β-Lactams 12−15 to Benzaldehyde
a Isolated yield. bAssayed by 1HN MR integration. c56% of β-lactam 15 was recovered. d51% of β-lactam 15 was recovered. eContaining 7% of two C5-epimers (75:25 d.r.) according 1H NMR.
Unfortunately, PMP- and Boc-protected 12−13 appeared completely inert under both reaction conditions showing that a strongly electron-withdrawing group attached to the nitrogen atom is necessary. However, N-Ms-azetidin-2-one 14 delivered expected allenediol 16 in 48% and 53% yield using N-MI and PY ligands, respectively, albeit with reduced 1,5-stereocontrol, as compared to reactions of N-Ts-β-lactam 1 depicted in Tables 1 and 2. Applying N-Ts-4-propynyl-azetidin-2-one 15, in turn, delivered the expected triply substituted allenediol 17, though in low yield in both cases due to only partial conversion of the substrate within 24 h. Since in our previous study on the reactions of 4-vinyl-β-lactams we have established that, in the case of less active substrates with a substituted vinyl moiety, the application of a THF/EtOH mixture instead of THF/ HMPA leads to much higher conversion,4c in additional experiments HMPA was replaced with ethanol. Under such modified conditions, full conversion of 15 was observed within 3 h and the desired allenediol 17 was obtained in high 73% and 71% yield using N-MI and PY, respectively. Unfortunately, although the directing effects of the ligands were still noticeable, in all of the conducted experiments, 2,6-antiepimer 17a was formed predominantly. Especially when N-MI in a 9:1 THF/EtOH mixture was applied, exceptionally efficient 2,6-anti-selectivity (85:15 d.r.) was observed. It is noteworthy that the obtained results stay in sharp contrast to
stereoselective C4−N β-lactam bond cleavage by Pd(PPh3)4 attack occurring from the opposite side of the C−N bond of the azetidin-2-one ring with inversion of configuration (SN2′) followed by reductive transmetalation of the transient πpropargylpalladium(II) species with the InI·N-MI or InI·PY complex,4c retaining the stereochemistry. Subsequently, allenylindium Ia or IIa generated in this manner (depending on whether cis- or trans-β-lactam was used) undergoes rapid stereospecific 1,3-rearrangement to the corresponding, apparently more stable trans- or cis-substituted cyclic ε-amidopropargylindium Ib or IIb, where the metal atom is situated in the usually unfavorable, more sterically hindered, γ-position as a consequence of the chelation of the indium atom with the εN-Ts-carboxamide group.11 Thus, the reactions take place on the terminal atom of the allenyl/propargyl system, which explains the observed unusual regioselectivity of the process. Assuming the addition to the aldehyde step occurs via bicyclic, rigid transition states ts-1−ts-2 and ts-3−ts-4 in the cases of εamido-propargylindiums Ib and IIb, respectively, all four C
DOI: 10.1021/acs.orglett.9b00891 Org. Lett. XXXX, XXX, XXX−XXX
Letter
Organic Letters analogous reactions of N-Ts-β-lactam 1 with an unsubstituted ethynyl group depicted in Table 1, where the experiments conducted in the THF/EtOH mixture led to much worse results as compared to those carried out in THF/HMPA. A number of methods were used to determine the configuration of the obtained allenediols (Scheme 4). While
carboxamido group, additions of these intermediates to aldehydes proceed with regioselectivity atypical for terminal secondary propargylindium reagents, with excellent central-toaxial chirality transfer and, in many cases, with a useful level of remote 1,5-asymmetric induction which can be altered by an N-ligand switch. Due to the presence of numerous functional groups in their structure, allenic diols obtained in this manner could serve as intermediates in the asymmetric synthesis of a variety of linear, carba- and heterocyclic organic compounds. Further elaboration of the chemistry presented, including exploration of alternative reaction conditions toward the elimination of the highly undesirable HMPA,7 as well as its application in asymmetric synthesis of other classes of derivatives and selected natural products is currently in progress.
Scheme 4. Synthesis of 2,6-Diol 18 and α-Allenyl Ketone 19 and 1,5-Dihydrofuranes 20a−20b
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ASSOCIATED CONTENT
S Supporting Information *
The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acs.orglett.9b00891. Experimental details, characterization data and 1H and 13 C NMR spectra for all new and selected known compounds, 19F NMR spectra for Mosher’s esters, HPLC chromatograms, and X-ray crystallographic data (PDF) Accession Codes a
b
CCDC 1895500−1895501 and 1902129 contain the supplementary crystallographic data for this paper. These data can be obtained free of charge via www.ccdc.cam.ac.uk/data_request/ cif, or by emailing
[email protected], or by contacting The Cambridge Crystallographic Data Centre, 12 Union Road, Cambridge CB2 1EZ, UK; fax: +44 1223 336033.
13
Isolated yield. Assayed by CNMR integration.
the reduction of double bonds in product 4b (78:22 d.r.) delivered 2,6-diol 18 as an inseparable mixture of two diastereomers in a 79:21 ratio, the oxidation of N-methylated derivative of 4b with DMP delivered α-allenyl ketone 19 as a virtually single diastereomer8 showing that allenes 4a and 4b differ only in the C6 function configuration. By comparison with previously reported 13C NMR spectra,4a it was established that the major isomer of 18 exhibits the 2,6-anti configuration. Stereospecific 5-endo-trig cyclization of allenediol 4b (78:22 d.r.)12 gave two 1,5-dihydrofurans 20a and 20b in 35% and 8% yield, where relative ring configurations were assigned as transand cis-, respectively, by NOE measurements.8 The relative configuration of 20b was further confirmed by X-ray analysis.8 On the basis of these arrangements, it was established that the adduct 4a and 4b configuration is 2,5-syn-2,6-anti- and 2,5-syn2,6-syn-, respectively. The configuration of allene 8b was determined directly by X-ray diffractometry.8 The configurations of other allenediols were assigned by analogy. It is noteworthy that the transformations presented in this paragraph are also examples of the application of the obtained allenediols in asymmetric synthesis. While linear 1,5-syn- and 1,5-anti- diols with remote stereogenic centers constitute 1,5polyol subunits,13 chiral α-allenyl ketones serve as intermediates for a variety of furans.1a,b Differently substituted 1,5dihydrofurans and their dihydro-derivatives are in turn the structural units of various polyene mycotoxins14 and polyether antibiotics.15 In summary, we demonstrated the utility of readily available N-Ts-4-ethynylazetidin-2-ones as precursors of chiral configurationally stable ε-amido-propargylindiums for the first time. Due to internal chelation of the indium atom with the N-Ts-
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AUTHOR INFORMATION
Corresponding Author
*E-mail:
[email protected]. ORCID
Bartosz K. Zambroń: 0000-0002-7170-4174 Present Address †
Faculty of Chemistry, University of Warsaw, Pasteura 1, 02093 Warsaw, Poland Notes
The authors declare no competing financial interest.
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ACKNOWLEDGMENTS We thank the National Science Centre for financial support, Grant SONATA UMO-2015/19/D/ST5/00713. REFERENCES
(1) (a) For selected books and reviews, see: (a) Modern Allene Chemistry; Krause, N., Hashmi, A. S. K., Eds.; WILEY-VCH: Weinheim, 2004. (b) Krause, N.; Winter, C. Gold-Catalyzed Nucleophilic Cyclization of Functionalized Allenes: A Powerful Access to Carbo- and Heterocycles. Chem. Rev. 2011, 111, 1994− 2009. (c) Ma, S. Some Typical Advances in the Synthetic Applications of Allenes. Chem. Rev. 2005, 105, 2829−2871. (2) For a recent review, see: Hoffmann-Röder, A.; Krause, N. Synthesis and Properties of Allenic Natural Products and Pharmaceuticals. Angew. Chem., Int. Ed. 2004, 43, 1196−1216. D
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to Amino Acids and Relevant Nitrogen-Containing Compounds. Top. Heterocycl. Chem. 2010, 22, 211−258. (6) Wang, C. Electrophilic Ring Opening of Small Heterocycles. Synthesis 2017, 49, 5307−5319 and references therein . (7) Due to confirmed acute toxicity in mammals and proven carcinogenicity towards rats, HMPA should be considered dangerous. Thus, all necessary precautions must be taken to avoid exposure to this chemical and, when possible, the use of safer substitutes such as DMPU or DMI is recommended. For details see: Dykstra, R. R. Hexamethylphosphoric Triamide. In Encyclopedia of Reagents for Organic Synthesis; Wiley: 2011, DOI: 10.1002/047084289X.rh020 and references therein. (8) See Supporting Information for details. (9) For selected reviews, see: (a) Ternansky, R. J.; Morin, J. M., Jr. In The Organic Chemistry of β-lactams; Georg, G. I., Eds.; VCH: New York, 1993; p 257. (b) Brandi, A.; Cicchi, S.; Cordero, F. M. Novel syntheses of azetidines and azetidinones. Chem. Rev. 2008, 108, 3988−4035. (c) Pitts, C. R.; Lectka, T. Chemical Synthesis of βLactams: Asymmetric Catalysis and Other Recent Advances. Chem. Rev. 2014, 114, 7930−7953. (d) Kamath, A.; Ojima, I. Advances in the chemistry of β-lactam and its medicinal applications. Tetrahedron 2012, 68, 10640−10664. (e) Magriotis, P. A. Progress in Asymmetric Organocatalytic Synthesis of β-Lactams. Eur. J. Org. Chem. 2014, 2014, 2647−2657. (f) Fu, N.; Tidwell, T. T. Preparation of β-lactams by [2 + 2] cycloaddition of ketenes and imines. Tetrahedron 2008, 64, 10465−10496. (10) For other examples of configurationally stable allenyl/propargyl indiums generated via transmetalation undergoing rapid 1,3rearrangement even in the presence of aldehydes, see ref 3b−d. (11) Due to significant oxophilicity of indium(III), alternative structures of intermediates Ib and IIb as well as transition states ts-1− ts-4 where the amide oxygen binds the indium (III) atom instead of the nitrogen could also be possible. (12) Marshall, J. A.; Bartley, G. S. Observations Regarding the Ag(I)-Catalyzed Conversion of Allenones to Furans. J. Org. Chem. 1994, 59, 7169−7171. (13) (a) Friestad, G. K.; Sreenilayam, G. 1,5-Polyols: Challenging motifs for configurational assignment and synthesis. Pure Appl. Chem. 2011, 83, 461−478 and references therein . (b) Friestad, G. K.; Sreenilayam, G. Versatile Configuration-Encoded Strategy for Rapid Synthesis of 1,5-Polyol Stereoisomers. Org. Lett. 2010, 12, 5016− 5019. (c) Flamme, E. M.; Roush, W. R. Enantioselective Synthesis of 1,5-anti- and 1,5-syn-Diols Using a Highly Diastereoselective One-Pot Double Allylboration Reaction Sequence. J. Am. Chem. Soc. 2002, 124, 13644−13645. (14) (a) Ganguli, M.; Burka, L. T.; Harris, T. Structural studies of the mycotoxin verrucosidin. J. Org. Chem. 1984, 49, 3762−3766. (b) Hatakeyama, S.; Sakurai, K.; Numata, H.; Ochi, N.; Takano, S. A novel chiral route to substituted tetrahydrofurans. Total synthesis of (+)-verrucosidin and formal synthesis of (−)-citreoviridin. J. Am. Chem. Soc. 1988, 110, 5201−5203. (c) Whang, K.; Cooke, R. J.; Okay, G.; Cha, J. K. Total synthesis of (+)-verrucosidin. J. Am. Chem. Soc. 1990, 112, 8985−8987. (15) Boivin, T. L. B. Synthetic routes to tetrahydrofuran, tetrahydropyran, and spiroketal units of polyether antibiotics and a survey of spiroketals of other natural products. Tetrahedron 1987, 43, 3309−3362.
(3) For selected reviews and articles on allylations and propargylations/allenylations with organoindiums, including Pd(0)/ InI methodology, see: (a) Shen, Z.-L.; Wang, S.-Y.; Chok, Y.-K.; Xu, Y.-H.; Loh, T.-P. Organoindium Reagents: The Preparation and Application in Organic Synthesis. Chem. Rev. 2013, 113, 271−401. (b) Marshall, J. A.; Grant, C. M. Formation of Transient Chiral Allenylindium Reagents from Enantioenriched Propargylic Mesylates through Oxidative Transmetalation. Applications to the Synthesis of Enantioenriched Homopropargylic Alcohols. J. Org. Chem. 1999, 64, 696−697. (c) Ohno, H.; Hamaguchi, H.; Tanaka, T. Umpolung of Chiral 2-Ethynylaziridines: Indium(I)-Mediated Stereoselective Synthesis of Nonracemic 1,3-Amino Alcohols Bearing Three Chiral Centers Catalyzed by Palladium(0). Org. Lett. 2000, 2, 2161−2163. (d) Ohno, H.; Hamaguchi, H.; Tanaka, T. 2-Ethynylaziridines as Chiral Carbon Nucleophiles: Stereoselective Synthesis of 1,3-Amino Alcohols with Three Stereocenters via Allenylindium Reagents Bearing a Protected Amino Group. J. Org. Chem. 2001, 66, 1867− 1875. (e) Haddad, T. D.; Hirayama, L. C.; Buckley, J. J.; Singaram, B. Indium-Mediated Asymmetric Barbier-Type Propargylations: Additions to Aldehydes and Ketones and Mechanistic Investigation of the Organoindium Reagents. J. Org. Chem. 2012, 77, 889−898. (f) Hirashita, T.; Suzuki, Y.; Tsuji, H.; Sato, Y.; Naito, K.; Araki, S. Nickel-Catalyzed Indium(I)-Mediated syn-Selective Propargylation of Aldehydes. Eur. J. Org. Chem. 2012, 2012, 5668−5672. (g) Cesario, C.; Miller, M. J. Pd(0)/InI-mediated allylic additions to 4-acetoxy-2azetidinone: new route to highly functionalized carbocyclic scaffolds. Org. Lett. 2009, 11, 1293−1295. (h) Takemoto, Y.; Anzai, M.; Yanada, R.; Fujii, N.; Ohno, H.; Ibuka, T. Stereoselective synthesis of nonracemic 1,3-amino alcohols from chiral 2-vinylaziridines by InI− Pd(0)-promoted metalation. Tetrahedron Lett. 2001, 42, 1725−1728. (i) Anzai, M.; Yanada, R.; Fujii, N.; Ohno, H.; Ibuka, T.; Takemoto, Y. Asymmetric synthesis of β2,3-amino acids by InI−Pd(0)-promoted metalation and addition of chiral 2-vinylaziridines. Tetrahedron 2002, 58, 5231−5239. (j) Araki, S.; Kameda, K.; Tanaka, J.; Hirashita, T.; Yamamura, H.; Kawai, M. Umpolung of vinyloxiranes: regio- and stereoselectivity of the In/Pd-mediated allylation of carbonyl compounds. J. Org. Chem. 2001, 66, 7919−7921. (k) Lee, W.; Kim, K.-H.; Surman, M. D.; Miller, M. J. Stereo- and regioselectivity of Pd(0)/InI-mediated allylic additions to aldehydes and ketones. In situ generation of allylindium(III) intermediates from N-acylnitroso DielsAlder cycloadducts and 1-amino-4-acetoxycyclopentenes. J. Org. Chem. 2003, 68, 139−149. (4) (a) Klimczak, U. K.; Zambroń, B. K. Effective 1,5-stereocontrol in Pd(0)/InI promoted reactions of chiral N-Ts-4-vinylazetidin-2ones with aldehydes. An efficient entry to nonracemic semi-protected (3Z)-2,6-anti-enediols. Chem. Commun. 2015, 51, 6796−6799. (b) Klimczak, U.; Staszewska-Krajewska, O.; Zambroń, B. K. Reverse regioselectivity in Pd(0)/InI-mediated allylation of aldehydes with εamido-allylindiums generated from β-lactams. A new entry to nonracemic highly substituted γ-butyrolactones. RSC Adv. 2016, 6, 26451−26460. (c) Plata, P.; Klimczak, U.; Zambroń, B. K. Acyclic Remote 1,5- and 1,4,5-Stereocontrol in the Catalytic Stereoselective Reactions of β-Lactams with Aldehydes: The Effect of the NMethylimidazole Ligand. J. Org. Chem. 2018, 83, 14527−14552. (5) For selected reviews see: (a) Ojima, I. In The Organic Chemistry of β-lactams; Georg, G. I., Eds.; VCH: New York, 1993; p 197. (b) Ojima, I.; Delaloge, F. Asymmetric synthesis of building-blocks for peptides and peptidomimetics by means of the β-lactam synthon metod. Chem. Soc. Rev. 1997, 26, 377−386. (c) Deshmukh, A. R. A. S.; Bhawal, B. M.; Krishnaswamy, D.; Govande, V. V.; Shinkre, B. A.; Jayanthi, A. Azetidin-2-ones, synthon for biologically important compounds. Curr. Med. Chem. 2004, 11, 1889−1920. (d) Alcaide, B.; Almendros, P. Beta-lactams as versatile synthetic intermediates for the preparation of heterocycles of biological interest. Curr. Med. Chem. 2004, 11, 1921−1949. (e) Alcaide, B.; Almendros, P.; Aragoncillo, C. β-Lactams: Versatile Building Blocks for the Stereoselective Synthesis of Non-β-Lactam Products. Chem. Rev. 2007, 107, 4437−4492. (f) Palomo, C.; Oiarbide, M. β-Lactam Ring Opening: A Useful Entry E
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