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Cinchona-Based Primary Amine Catalyzed a Proximal Functionalization of Dienamines: Asymmetric #-Fluorination of #-Branched Enals Satoru Arimitsu, Tsunaki Yonamine, and Masahiro Higashi ACS Catal., Just Accepted Manuscript • Publication Date (Web): 14 Jun 2017 Downloaded from http://pubs.acs.org on June 14, 2017
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ACS Catalysis
Cinchona-Based Primary Amine Catalyzed a Proximal Functionalization of Dienamines: Asymmetric a-Fluorination of a-Branched Enals Satoru Arimitsu*, Tsunaki Yonamine and Masahiro Higashi* Department of Chemistry, Biology and Marine Science, University of the Ryukyus, Senbaru 1, Nakagami, Nishihara, Okinawa, 903-0213, Japan
ABSTRACT: Fluorination of dienamines generated by a-branched enals and 6’-hydroxy-9-amino-9-deoxy-epi-quinidine (30 mol%) with NSFI showed excellent a-regioselectivity to construct allylic fluorides containing a highly stereocontrolled quaternary fluorinated carbon (E/Z = >20/1 and up to 93% ee). By DFT calculation, the quinuclidine moiety of the catalyst was shown to function as a coordinating group to promote a reaction at the proximal a-position, and the non-classical CH hydrogen bond plays an important role in the high enantioselectivity.
KEYWORDS: dienamine, organocatalysis, fluorinated quaternary carbon, allylic fluoride, CH hydrogen bond
Throughout the long history of organic chemistry, the organic reactions related to vinylogous motifs have been considered one of the fundamental chemical transformations.1 New synthetic methodologies have been developed to control the regio- and stereoselectivity of vinylogous reactants; for example, the vinylogous aldol reaction with transition-metal catalysts is a notable well-established asymmetric transformation.2 Recently, asymmetric aminocatalysis has been applied for vinylogous principles using g-enolizable a,b-unsaturated aldehydes, and controlling the reaction site of dienamine intermediates has progressed along with the development of new catalysts. Namely, asymmetric reactions at the g-position, the remote reaction site, have flourished with several successful precedents.3 In contrast, the a-position, the proximal reaction site, has received lesser attention,4 and no successful example of a-quaternary stereocenter with high stereoselectivity has been reported to date R' R" E
R' R
R
N H
R"
R'
aminocatalyst
CHO
N α R γ dienamine intermediate
R, R' and/or R" = Aryl, Alkyl, H
(Scheme 1).5
R"
E+
* CHO α α-selective
R' E
R"
R *γ CHO γ-selective
Scheme 1. General aminocatalytic reactions of g-enolizable a,b-unsaturated aldehydes with an electrophile (E+).
The strategies for controlling the regioselectivity of a dienamine are summarized in Figure 1. Control by steric hindrance of a substrate has sometimes been quite successful (top, Figure 1).4b-e Moreover, we applied this methodology for the regio- and stereoselective synthesis of a,a-difluoro-g,g-disubstituted butenals, of which fluorination can proceed at only a-position due to the steric hindrance of the substrates on g-position;6 however, it is inherently not possible to cause a reaction at a sterically hindered reaction site, for example, constructing a quaternary substituted carbon. The steric hindrance of catalysts has also been utilized to differentiate reaction sites, though the reaction has an electrophile size limitation (middle, Figure 1); bulky electrophiles are required to attain excellent stereoselectivity.7 Finally, the use of coordinating groups in the catalyst structure appears to be one of the most promising methods to control the reaction site (bottom, Figure 1). In fact, the Melchiorre group recently demonstrated the power of a coordinating group to promote a reaction at only the g-position with high enantioselectivity.8 It was believed that the phenolic hydroxyl group of 6’-hydroxy-9-amino-9-deoxy-epi-quinidine could coordinate an external Brønsted acid through the hydrogen-bonding network to lead electrophiles close to the g-position.8b Although several other good methodologies have been developed to promote a reaction at the remote g-position of dienamine intermediates,3, 9 no successful strategy has been reported for a reaction at a proximal a-position of a-branched enal with high stereoselectivity. While the guiding ability of the phenolic hydroxyl group of cinchona-based primary amine catalysts has been investigated, the quinuclidine moiety has also been suggested to coordinate with electrophiles by some studies, despite the lack of conclu-
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sive evidence.10 In fact, recent DFT calculation of the a-fluorination of cyclic ketones with cinchona-based primary amine catalysts has indicated that the fluorination can occur in an intramolecular fashion through the N-fluorinated quinuclidine moiety.11 This research encourages us to examine if the quinuclidine nitrogen moiety of cinchona-based primary amine catalysts can indeed act as a coordinating group and lead electrophiles, such as fluorine, toward the proximal position of dienamine intermediates. (i) by steric hindrance of a substituent
R"
R γ
α
R' N
R γ
Table 1. Screening of reaction conditions.a Me Ph
+
PhO2S
CHO 1a (1.0 equiv)
catalyst (30 mol%) acid (60 mol%)
SO2Ph
DMF (0.25 M), r.t., Time (h)
F Me Ph
CHO 2a
Catalyst R
R'
X
OH N
N
NH2
N
α
N F
NFSI (1.5 equiv)
C1: R = Ph, R' = Me C2: R = Ph, R' = CO2H C3: R = CH2Ph, R' = CO2H
E+
E+
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(ii) by steric hindrance of a catalyst
NH2
H2N N
N
C9
C4: X = OH, Y = H C5: X = OMe, Y = H Y C6: X = OMe, Y = Ph C7: X = OMe, Y = 3,5-(CF3)2-C6H3 C8: X = H, Y = H
Acid
E+ γ
R
α
A1: p-TsOH A2: MeSO3H A3: PhCO2H
N
O
O
O
P
A4: O
O P
A5: OH
O
OH
(iii) by a coordinating group (CG) of a catalyst E+
E+
CG
CG
E/Zd
ee (%)e
trace
N.Df
N.Df
>48
trace
N.Df
N.Df
A1
>48
trace
N.Df
N.Df
C4
A1
15
45
2.3/1
77
5
C5
A1
15
52
1.5/1
71
6
C6
A1
21
49
1.2/1
71
7
C7
A1
19
46
1.6/1
63
C8
A1
15
41
1.5/1
74
C4
A1
12
51
1.5/1
78
10g
C4
A2
21
49
2.6/1
75
g
C4
A3
>72
42
6.7/1
66
12g
C4
A4
18
58
5.1/1
79
g
C4
A5
18
58
5.7/1
72
14g, h
C4
A4
>120
38
15/1
91
15g, h, i
C4
A4
80
79 (71)
>20/1
91
16g, h, i
C9
A5
80
76 (70)
>20/1
–91
acid
1
C1
A1
>48
2
C2
A1
Figure 1. The strategies for controlling the regioselectivity of dienamine intermediates.
3
C3
4
To investigate this hypothesis, the dienamine intermediates of a-branched enals can be selected as ideal models, because DFT calculation shows that the dienamine intermediates generated with (2E)-2-methyl-4-phenylbut-2-enal 1a and 6’-hydroxy-9-amino-9-deoxy-epi-quinidine C4 possess stronger nucleophilicity at the g-position based on both the electrostatic potential (ESP) distribution and natural population analysis (NPA) charges (Figure 2).12, 13 This result clearly indicates the difficulty of reaction at the a position; thus, the a-regioselective reaction of dienamine generated from a-branched enals requires assistance to overcome not only steric hindrance but also weaker nucleophilicity. Herein, we wish to report the highly enantioselective proximal a-fluorination of a-branched enals14 and reveal how the quinuclidine nitrogen moiety of cinchonabased primary amine catalysts can function as a coordinating group also control each selectivity.
R γ
α
R" N
remote control
Cg
R γ
α
entry
time (h)b
catalyst
R"
yield (%)c
N
proximal control (this work)
8 9
g
11
13
a
Ca
Unless otherwise specified, the reaction was performed in DMF (0.25 M) at room temperature. bDetermined by monitoring the consumption of 1a by TLC. cDetermined by 19F NMR spectroscopy using PhOCF3 as an internal standard, and the values in the parentheses are the isolated yield of 2a. dDetermined by 1H NMR analysis of the crude material. eDetermined by HPLC equipped with Daicel Chiralpak, IA-3 after reductive amination. f Not determined. gNMP was used instead of DMF. hat –25 °C. i with 40 equiv of H2O.
The values of NPA • Ca: –0.164 • Cg: –0.304 (isosurface: –0.049 au)
Figure 2. ESP distribution of the dienamine intermediate of aldehyde 1a and catalyst C4, also NPA charges of Ca and Cg calculated at SMD-M06-2X/6-31G(d,p) level.
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The reaction screening commenced with the fluorination of a-branched enal 1a with various catalysts as summarized in Table 1.
Table 2. Substrate scope.a
R2
The non-functional chiral primary amine C1 resulted in a very slow reaction and yielded just a trace amount of target product 2a with complicated fluorinated byproducts revealed by 19F NMR—probably the mixture of stereoisomers (entry 1). Bifunctional primary amines, such as amino acids, gave a similar reaction outcome (entry 2-3). However, consistent with our assumption about the coordinating function of the quinuclidine nitrogen moiety, all primary amines derived from cinchonine and quinidine provided only a-regioisomer with good enantioselectivity even in low yield and E/Z stereoselectivity (entries 4-8).15 Interestingly, substantial solvent effects were observed; that is, only polar aprotic solvents, such as DMF and NMP, gave good enantioselectivity (entries 4 and 9, see other solvents in the Supporting Information). Brønsted acid additives had a positive influence on the reaction efficiency and stereoselectivity, and among all Brønsted acids tested, A4 gave the best stereoselectivity (up to 79% ee with a E/Z ratio of 5.1/1, entry 12, see other Brønsted acids in the Supporting Information). It is noteworthy that the stereoinduction of this reaction is highly controlled by aminocatalyst and is slightly influenced by the configuration of the chiral Brønsted acids (see the comparison of entries 12 and 13). To attain better selectivity, the reaction was conducted at –25 °C, drastically improving the E/Z- and enantioselectivity even though the reaction was extremely slowed (entry 14). To shorten the reaction time, 40 equivalents of water were added and had a significant effect;16 the reaction maintained a-regioselectivity and gave good yield with excellent E selectivity (E/Z = >20/1) and enantioselectivity up to 91% ee (entry 15). This reaction condition can be applied to the primary amine catalyst derived from quinine C9, pseudoenantiomer of C4, which gave good yield of corresponding product 2a as the opposite enantiomer in excellent enantioselectivity (–91% ee) and E selectivity (E/Z = >20/1) using A5 (entry 16).17 After the optimum reaction conditions were determined, we examined the scope of the reaction with respect to substrates of a-branched enals; all reactions gave the corresponding a-fluorinated aldehydes 2 with excellent a-regioselectivity and stereoselectivity in good to moderate yields (Table 2). Generally, either electron-withdrawing or electron-donating groups on the aromatic ring of R1 did not influence the stereoselectivity; all gave excellent E selectivity (E/Z = >20/1) and enantioselectivity up to 93% ee (entries 2-6). The aromatic groups with sterically hindered substrates were well tolerated in these conditions to give similar outcomes (entries 7-9). In the case of the aliphatic group on R1 or the bulkier Et on R2, the reactions were very sluggish with moderate enantioselectivity; however, they yielded only a-regioisomers and excellent E selectivity (entries 10-11).
R1
+
PhO2S
CHO
N F
SO2Ph
NMP (0.25 M), –25 °C, time (h)
NFSI (1.5 equiv)
1 (1.0 equiv)
R1
entry
catalyst: C4 (30 mol%) acid: A4 (60 mol%) H2O (40 equiv)
F R2 R1
CHO
2 only α-regioisomer
R2
time (h)b
yield (%)c
E/Zd
ee (%)e
1
C6 H5
Me
80
2a: 79 (71)
>20/1
91
2
4-F-C6H4
Me
89
2b: 71 (66)
>20/1
90
3
4-Cl-C6H4
Me
81
2c: 80 (70)
>20/1
90
4
4-Br-C6H4
Me
90
2d: 64 (61)
>20/1
91
5
4-Me-C6H4
Me
96
2e: 86 (75)
>20/1
92
6
4-t-Bu-C6H4
Me
96
2f: 56 (53)
>20/1
93
7
3-Me-C6H4
Me
73
2g: 70 (63)
>20/1
87
8
2-Me-C6H4
Me
99
2h: 62 (61)
>20/1
90
1-naphtyl
Me
102
2i: 66 (65)
>20/1
92
PhCH2
Me
168
2j: 44 (42)
>20/1
81
C6 H5
Et
240
2k: 48 (47)
>20/1
77
9 10 11
f
a
The reaction was performed with 1 (0.1 mmol), NFSI (0.15 mmol) in the presence of C4 (30 mol%) and A4 (60 mol%) in NMP (0.25 M) and H2O (40 equiv) at –25 °C. bDetermined by monitoring consumption of 1 by TLC. cDetermined by 19F NMR spectroscopy using PhOCF3 as an internal standard, and the values in the parentheses are the isolated yield of 2. dDetermined by 1 H NMR analysis of the crude material. eDetermined by HPLC equipped with a chiral stationary phase after reductive amination. f at 0 °C.
The stereochemistry and absolute configuration of the product were unambiguously determined to be the E-stereoisomer and R-configuration by single-crystal X-ray diffraction analysis of a derivative of 2d (Figure 3). The structures of all other compounds were determined by comparison with the 1H and 19F NMR of 2d.
F Me Bn N
Br
O
Br
derivative of 2d ee: >99% after recrystallization
Figure 3. ORTEP diagram of a derivative of 2d. Ellipsoids displayed at 50% probability.
Next, with the absolute structure of compound 2 in hand, the details of the reaction mechanism were investigated with the aid of DFT calculations at the SMD-M06-2X/6-31G(d,p) level; all
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the calculations were performed using Gaussian 09.18 The similar enantioselectivities were obtained using Brønsted acids A2 and A4 with aminocatalyst C4, 75% and 79% ee, respectively (entries 10 and 12 in Table 1), therefore DFT calculation was conducted using A2 due to lesser computational time. As per the previous study,11 the dienamine with catalyst C4 gives two possible transition state structures in the presence of NFSI and Brønsted acid A2 in DMF (Figure 4). The location of the fluorine atom on quinuclidine is much closer to the a than the g position of the dienamine through a seven-membered ring intramolecular interaction, which is the origin of the high a-regioselectivity. Interestingly, the activation free energy of TS-R is slightly lower than that of TS-S when in the presence of the counter ion MeSO3−. This result indicates that MeSO3− preferentially stabilizes the TS-R configuration, even though the hydrogen bond between the N-H of dienamine and the Lewis basic oxygen OS of MeSO3− is weaker and the distance of a fluorine atom to Ca is longer than to those of TS-S. Further detailed analysis revealed a considerable contribution of non-classical C-H···O hydrogen bonds to the stabilization of the TS-R configuration summarized in the table of Figure 4 (see the Supporting Information for details).19 The distance of the Cβ-H···OS hydrogen bond at TS-R, 2.232 Å, is the typical distance of a CH···O hydrogen bond, and much shorter than the CMe-H···O′S distance at TS-S, 2.422 Å (O′S is another oxygen of MeSO3−, closest to CMe-H).
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hydrogen bond between Cβ-H and MeSO3− is crucial for high enantioselectivity.21, 22 Finally, the high E configuration on double bond originates from the thermodynamic control considering the steric hindrance between Mea and Phg. Interesting acceleration of the reaction by water was also examined by DFT calculation, which revealed that water used as a solvent decreases activation free energy of TS-R to 10.24 kcal/mol compared with 16.37 kcal/mol in DMF due to stabilization of ionic TS-R by strong polarity of water. More detailed analysis, such as effects of the counter ion and solvent on the reaction mechanism, are in progress. In conclusion, we have developed a new synthetic methodology for proximal a-regioselective fluorination of a-branched enals, which provides allylic fluorides bearing a quaternary fluorinated carbon in good yield and high E-selectivity and enantioselectivity. This reaction can expand the structural diversity of allylic fluorides.23 In addition, DFT calculation clarified that the quinuclidine moiety can indeed function as the coordinating group to promote a nucleophilic reaction at the a-position of dienamine intermediates and that a conjugate base of a Brønsted acid can modulate the stereochemistry of dienamine intermediates through the non-classical CH hydrogen bond network. These results can be a good complement to g-selective nucleophilic reactions of dienamine catalysis and can enrich vinylogous chemistry using organocatalysis.
AUTHOR INFORMATION 1.90 2.24 Ca
Cb Cph
1.90 N 2.20
Os
Ca
TS-R (major)
State
DG‡
TS-R
16.37
TS-S
16.93
Corresponding Author
O’s
N
CMe
Os
TS-S (minor) Hydrogen bond
Distance of H···Os (Å)
Bond order
N-H···OS
1.910
0.0386
Cβ-H···OS
2.232
0.0141
CPh-H···OS
2.471
0.0091
N-H···OS
1.880
0.0507
CMe-H···O′S
2.422
0.0099
Figure 4. Calculated TS structures and activation free energies (in kcal/mol) for dienamines generated from 1a and catalyst C4 in the presence of NFSI and A2 in DMF. The important CH hydrogen bonds are shown in the figures.
The Wiberg bond order analysis in the natural atomic orbital (NAO) basis showed that the large bond order of Cβ-H···OS at TS-R (0.0141) compared with that of CMe-H···O′S at TS-S (0.0099).20 The second-order perturbation theory analysis of the Fock matrix in the natural bonding orbital (NBO) basis also showed that the interaction energy due to the charge transfer from the OS lone pair to the Cβ-H σ* orbital at TS-R (2.56 kcal/mol) is larger than that from the O′S lone pair to the CMe-H σ* orbital at TS-S (1.17 kcal/mol).20 These results are consistent with several previous studies indicating that the C-H donor strength depends on the carbon hybridization as C(sp2)-H > C(sp3)-H.19 Therefore, we concluded that the non-classical CH
E-mail:
[email protected] (for synthesis) E-mail:
[email protected] (for DFT calculation)
Funding Sources This work was supported by MEXT/JSPS KAKENHI (Grant Numbers: JP16H00778, JP16KT0165, JP17K05757 and JP17K14451). and partially by a grant from Institute of Quantum Chemical Exploration and Okinawa Intellectual Cluster Program.
ASSOCIATED CONTENT Supporting Information The Supporting Information is available free of charge on the ACS Publications website. Experimental part including general reaction method, characterization data, NMR spectra, HPLC data, single-crystal X-ray diffraction analysis and DFT calculation. (PDF) Crystallographic data for a derivative of 2d, C25H22Br2FNO (CIF)
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ACKNOWLEDGMENT The authors thank Prof. Fujie Tanaka at Okinawa Institute of Science and Technology Graduate University for help with HRMS. The computations were performed at the Research Center for Computational Science, Okazaki, Japan.
REFERENCES (1) (a) Fuson, R. C. Chem. Rev. 1935, 16, 1–27. (b) Chinchilla, R.; Nájera, C. Chem. Rev. 2000, 100, 1891–1928. (2) (a) Casiraghi, G.; Battistini, L.; Curti, C.; Rassu, G.; Zanardi, F. Chem. Rev. 2011, 111, 3076–3154. (b) Denmark, S. E.; Heemstra, J. R.; Beutner, G. L. Angew. Chem. Int. Ed. 2005, 44, 4682–4698. (c) Casiraghi, G.; Zanardi, F.; Appendino, G.; Rassu, G. Chem. Rev. 2000, 100, 1929–1972. (3) For recent reviews, see: (a) Hepburn, H. B.; Dell’Amico, L.; Melchiorre, P. Chem. Rec. 2016, 16, 1787-1806. (b) Marcos, V.; Alemán, J. Chem. Soc. Rev., 2016, 45, 6812-6832. (c) Jiang, H.; Albrecht, Ł.; Jørgensen, K. A. Chem. Sci. 2013, 4, 2287–2300. (d) Jurberg, I. D.; Chatterjee, I.; Tannert, R.; Melchiorre, P. Chem. Commun. 2013, 49, 4869–4883. (e) Melchiorre, P. Angew. Chem. Int. Ed. 2012, 51, 9748–9770. (f) Ramachary, D. B.; Reddy, Y. V. Eur. J. Org. Chem. 2012, 865–887. And more related references cited therein. (4) (a) Hong, B.-C.; Chen, P.-Y.; Kotame, P.; Lu, P.-Y.; Lee, G.H.; Liao, J.-H. Chem Commun., 2012, 48, 7790-7792. (b) Enders, D.; Yang, X.; Wang, C.; Raabe, G.; Runsik, J. Chem.-Asian J. 2011, 6, 2255-2259. (c) Stiller, J.; Margués-López, E.; Herrera, R. P.; Fröhlich, R.; Strohmann, C.; Christmann, M. Org. Lett. 2011, 13, 70–73. (d) Han, B.; Xiao, Y.-C.; Yao, Y.; Chen, Y.-C. Angew. Chem. Int. Ed. 2010, 49, 10189-10191. (e) Han, B.; Xiao, Y.-C.; He, Z.-Q.; Chen, Y.-C. Org. Lett. 2009, 11, 4660–4663. (f) Margués-López, E.; Herrera, R. P.; Marks, T.; Jacobs, W. C.; Könning, D.; de Figueiredo, R. M.; Christmann, M. Org. Lett. 2009, 11, 4116-4119. (g) Utsumi, N.; Zhang, H.; Tanaka, F.; Barbas III, C. F. Angew. Chem. Int. Ed. 2007, 46, 1878-1880. (5) a-functionalization of a-branched enals had been sporadically investigated, see: Demoulin, N.; Lifchits, O.; List, B. Tetrahedron 2012, 68, 7568–7574. (6) Arimitsu, S.; Nakasone, M. J. Org. Chem., 2016, 81, 67076713. (7) (a) Cassani, C.; Melchiorre, P. Org. Lett. 2012, 14, 5590–5593. (b) Silvi, M.; Cassani, C.; Moran, A.; Melchiorre, P. Helv. Chim. Acta 2012, 95, 1985–2006. (8) (a) Bencivenni, G.; Galzerano, P.; Mazzanti, A.; Bartoli, G.; Melchiorre, P. Proc. Natl. Acad. Sci. U.S.A. 2010, 107, 20642–20647. (b) Bergonzini, G.; Vera, S.; Melchiorre, P. Angew. Chem. Int. Ed. 2010, 49, 9685–9688. (9) Additional notable references to ref 3 are following, see: (a) Kutwal, M. S.; Appayee, C. Eur. J. Org. Chem. 2017, DOI: 10.1002/ejoc.201700645. (b) Ran, G.-Y.; Gong, M.; Yue, J.-F.; Yang, X.-X.; Zhou, S.-L.; Du, W.; Chen, Y.-C. Org. Lett. 2017, 19, 18741877. (c) Di Iorio, N.; Righi, P.; Mazzanti, A.; Mancinelli, M.; Ciogli, A.; Bencivenni, G. J. Am. Chem. Soc. 2014, 136, 10250–10253. (d) Bastida, D.; Liu, Y.; Tian, X.; Escudero-Adán, E.; Melchiorre, P. Org. Lett. 2013, 15, 220–223. (10) Lifchits, O.; Demoulin, N.; List, B. Angew. Chem. Int. Ed. 2011, 50, 9680–9683. (11) Lam, Y. H.; Houk, K. N. J. Am. Chem. Soc. 2014, 136, 9556– 9559. (12) A similar evaluation of nucleophilicity was performed for vinylogous silyl enol ether, see: Ratjen, L.; García-García, P.; Lay, F.; Beck, M. E.; List, B. Angew. Chem. Int. Ed. 2011, 50, 754–758. (13) The nucleophilicity is often discussed in terms of condensed Fukui functions. However, the Fukui functions at the Ca and Cg atoms calculated from the HOMO orbital are very similar, ~0.20. Therefore,
we concluded that the HOMO orbital is not a dominant factor for the nucleophilicity. (14) It is worth noting that the challenges of this reaction are not only regioselectivity and stereoselectivity but also chemoselectivity (e.g. self-condensation), see: (a) Hong, B.-C.; Wu, M.-F.; Tseng, H.C.; Huang, G.-F.; Su, C.-F.; Liao, J.-H. J. Org. Chem. 2007, 72, 8459–8471. (b) Bertelsen, S.; Marigo, M.; Brandes, S.; Dinér, P.; Jørgensen, K. A. J. Am. Chem. Soc. 2006, 128, 12973–12980. (c) Bench, B. J.; Liu, C.; Evett, C. R.; Watanabe, C. M. H. J. Org. Chem. 2006, 71, 9458–9463. (15) The catalysts C6 and C7 were prepared by the procedure in the following papers, see: (a) Li, J.; Du, T.; Zhang, G.; Peng, Y. Chem. Commun. 2013, 49, 1330-1332. (b) Lee, A.; Reisinger, C. M.; List, B. Adv. Synth. Catal. 2012, 354, 1701–1706. (c) Lee, A.; Michrowska, A.; Sulzer-Mosse, S.; List, B. Angew. Chem. Int. Ed. 2011, 50, 1707–1710. (d) Hintermann, L.; Schmitz, M.; Englert, U. Angew. Chem. Int. Ed. 2007, 46, 5164–5167. (16) Jung, Y.; Marcus, R. A. J. Am. Chem. Soc. 2007, 129, 54925502. (17) The combination of C9 and A4 under this reaction condition gave the product 2a in –88% ee. (18) Gaussian 09, Revision D.01, Frisch, M. J.; Trucks, G. W.; Schlegel, H. B.; Scuseria, G. E.; Robb, M. A.; Cheeseman, J. R.; Scalmani, G.; Barone, V.; Mennucci, B.; Petersson, G. A.; Nakatsuji, H.; Caricato, M.; Li, X.; Hratchian, H. P.; Izmaylov, A. F.; Bloino, J.; Zheng, G.; Sonnenberg, J. L.; Hada, M.; Ehara, M.; Toyota, K.; Fukuda, R.; Hasegawa, J.; Ishida, M.; Nakajima, T.; Honda, Y.; Kitao, O.; Nakai, H.; Vreven, T.; Montgomery, J. A., Jr.; Peralta, J. E.; Ogliaro, F.; Bearpark, M.; Heyd, J. J.; Brothers, E.; Kudin, K. N.; Staroverov, V. N.; Kobayashi, R.; Normand, J.; Raghavachari, K.; Rendell, A.; Burant, J. C.; Iyengar, S. S.; Tomasi, J.; Cossi, M.; Rega, N.; Millam, M. J.; Klene, M.; Knox, J. E.; Cross, J. B.; Bakken, V.; Adamo, C.; Jaramillo, J.; Gomperts, R.; Stratmann, R. E.; Yazyev, O.; Austin, A. J.; Cammi, R.; Pomelli, C.; Ochterski, J. W.; Martin, R. L.; Morokuma, K.; Zakrzewski, V. G.; Voth, G. A.; Salvador, P.; Dannenberg, J. J.; Dapprich, S.; Daniels, A. D.; Farkas, Ö.; Foresman, J. B.; Ortiz, J. V.; Cioslowski, J.; Fox, D. J. Gaussian, Inc., Wallingford CT, 2009. (19) For selected papers for non-classical CH hydrogen bond, see: (a) Cai, J.; Sessler, J. L. Chem. Soc. Rev., 2014, 43, 6198-6213. (b) Scheiner, S.; Grabowski, S. J.; Kar, T. J. Phys. Chem. A, 2001, 105, 10607-10612. (c) Gu, Y.; Kar, T.; Scheiner, S. J. Am. Chem. Soc. 1999, 121, 9411-9422. (d) Steiner, T.; Desiraju, G. R. Chem. Commun. 1998, 891-892. (e) Steiner, T. Chem. Commun. 1997, 727-734. (20) (a) Weinhold, F.; Landis, C. R. Valency and Bonding: A Natural Bond Orbital Donor-Acceptor Perspective, Cambridge University Press, New York, 2005. (b) Reed, A. E.; Curtiss, L. A.; Weinhold, F. Chem. Rev. 1988, 88, 899-926. (21) The non-classical CH hydrogen bond has been reported to play an important role for high enantioselective catalysis, see: (a) Johnston, R. C.; Cheong, P. H.-Y.; Org. Biomol. Chem. 2013, 11, 5057-5064. (b) Zhang, W.; Tan, D.; Lee, R.; Tong, G.; Chen, W.; Qi, B.; Huang, K.-W.; Tan, C.-H.; Jiang, Z. Angew. Chem. Int. Ed. 2012, 51, 10069-10073. (22) The phosphates can also have a C-H···O hydrogen bond, see recent review: Jindal, G.; Kisan, H. K.; Sunoj, R. B. ACS Catal. 2015, 5, 480-503. And more reference cited therein. (23) The recent organocatalyzed asymmetric syntheses for allylic fluorides, see; (a) Neel, A. J.; Milo, A.; Sigman, M. S.; Toste, F. D. J. Am. Chem. Soc. 2016, 138, 3863-3875. (b) Zi, W.; Wang, Y.-M.; Toste, F. D. J. Am. Chem. Soc. 2014, 136, 12864-12867. (c) Wu, J.; Wang, Y.-M.; Drljevic, A.; Rauniyar, V.; Phipps, R. J.; Toste, F. D. Proc. Natl. Acad. Sci. U.S.A. 2013, 110, 13729-13733. (d) Phipps, R. J.; Toste, F. D. J. Am. Chem. Soc. 2013, 135, 1268-1271. (e) Shunatona, H. P.; Früh, N.; Wang, Y.-M.; Rauniyar, V.; Toste, F. D. Angew. Chem. Int. Ed. 2013, 52, 7724-7727.
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allyl fluorides with a-quaternary carbon
DFT revealed the origin of selectivities
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