LETTER
Asymmetric Mukaiyama Aldol Reaction
905
the aldehyde moiety of glyoxal was bound in the equato-
rial position. Enolsilane attacked from the less hindered
Si-face to afford the corresponding S product, since the
R. A. Acc. Chem. Res. 2000, 33, 432. (d) Palomo, C.;
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2
,6-diethylphenyl group on the ligand effectively shielded
2
009, 3661. (g) Geary, L. M.; Hultin, P. G. Tetrahedron:
the other face. While in TS2, the ketone group located at
the equatorial position which resulted in the steric hin-
drance between R of the substrate and the 2,6-diethylphe-
nyl group of the ligand.
Asymmetry 2009, 20, 131.
(
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(
1
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Si face attack
Ar
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R
OTMS
O
(e) Krüger, J.; Carreira, E. M. J. Am. Chem. Soc. 1998, 120,
O
N
837. (f) Evans, D. A.; Kozlowski, M. C.; Murry, J. A.;
HN
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Ni
O
O
NH
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TS1 favorable
Re face attack
Ar
(
k) Kiyooka, S.; Matsumoto, S.; Shibata, T.; Shinozaki, K.
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OTMS
(
O
R
O
N
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Ni
O
O
HN
NH
O
N
2006, 45, 6130. (e) Adachi, S.; Harada, T. Org. Lett. 2008,
1
0, 4999. (f) Gondi, V. B.; Hagihara, K.; Rawal, V. H.
TS2 disfavorable
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Figure 1 Proposed transition state for Mukaiyama aldol reaction
In summary, we have developed an efficient chiral L7–
Ni(II) complex catalyst for the enantioselective Mukai-
yama aldol reaction of glyoxal derivatives as well as gly-
oxylate. Excellent enantioselectivities (up to 95% ee) and
moderate to high yields (up to 95%) were obtained for a
range of substrates. Meanwhile, a proposed transition
state was depicted. Further efforts are being devoted to ap-
plying the catalyst to other reactions.
(
5) (a) Evans, D. A.; MacMillan, D. W. C.; Campos, K. R.
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Supporting Information for this article is available online at
http://www.thieme-connect.com/ejournals/toc/synlett.
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(
7) For examples of our recent work, see: (a) Zheng, K.; Shi, J.;
Liu, X. H.; Feng, X. M. J. Am. Chem. Soc. 2008, 130,
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L. L.; Feng, X. M. Chem. Commun. 2010, 46, 3771.
(c) Xie, M. S.; Chen, X. H.; Zhu, Y.; Gao, B.; Lin, L. L.; Liu,
X. H.; Feng, X. M. Angew. Chem. Int. Ed. 2010, 49, 3799.
(d) Hui, Y. H.; Jiang, J.; Wang, W. T.; Chen, W. L.; Cai, Y.
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Acknowledgment
We appreciate the financial support from the National Natural Sci-
ence Foundation of China (Nos. 20732003 and 20902060), PCSIRT
(
(
No. IRT0846), and the National Basic Research Program of China
973 Program: No. 2010CB833300). We also thank Sichuan Uni-
versity Analytical & Testing Center for NMR analysis.
2
010, 49, 4290. (e) Li, W.; Wang, J.; Hu, X. L.; Shen, K.;
References and Notes
Wang, W. T.; Chu, Y. Y.; Lin, L. L.; Liu, X. H.; Feng, X. M.
J. Am. Chem. Soc. 2010, 132, 8532.
(
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Chem. Eur. J. 1998, 4, 1137. (b) Nelson, S. G. Tetrahedron:
Asymmetry 1998, 9, 357. (c) Denmark, S. E.; Stavenger,
(
8) Terada, M.; Soga, K.; Momiyama, N. Angew. Chem. Int. Ed.
2008, 47, 4122.
Synlett 2011, No. 7, 903–906 © Thieme Stuttgart · New York