Enantioselective Conjugate Addition
5507 – 5516
Conclusion
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We described in this paper an efficient catalytic ligand
system for the enantioselective conjugate addition of dieth-
[
I
ylzinc to enones catalyzed by Cu and axially chiral binaph-
thylthiophosphoramides, which are easily available, quite
stable, recoverable and reusable. The system allows efficient,
catalytic and highly enantioselective functionalization of not
only six and seven-membered cyclic enones (97% ee), but
also of cyclopentenone (98% ee) and acyclic enones (up to
5263; c) O. Huttenloch, E. Laxman, H. Waldmann, Chem. Commun.
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2
001, 343, 450–454); e) O. Pamies, G. Net, A. Ruiz, C. Claver, Tetra-
9
7% ee). Moreover, other zinc reagents such as Me Zn and
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2
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2
tion, most of the reactions can be completed under mild
conditions (20 or 08C) within 10–30 min. To the best of our
knowledge, the enantioselectivities and reaction rates ach-
ieved here are one of the best yet results for the Cu-cata-
lyzed enantioselective conjugate addition to enones. In addi-
tion, we confirmed that this series of chiral phosphoramides
1
3
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3
1
was a novel type of S,N-bidentate ligands through P NMR,
C NMR spectroscopic experiments. We deduced that the
13
mechanism of asymmetric Michael addition in our reaction
system may be a bimetallic catalytic process and the acidic
proton (H) of thiophosphoamide in the ligands plays a sig-
nificant role in the formation of the active species. The
linear effect of product ee and ligand ee further revealed
3
8, 3518–3521; o) R. Shintani, G. C. Fu, Org. Lett. 2002, 4, 3699–
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18; q) I. Chataigner, C. Gennari, S. Ongeri, U. Piarulli, S. Ceccarel-
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Pytkowicz, S. Roland, P. Mangeney, Tetrahedron: Asymmetry 2001,
I
that the active species is a monomeric Cu complex bearing
a single ligand [Cu :ligand 1:1].
I
1
2, 2087–2089; u) A. Alexakis, J. Vastra, P. Mangeney, Tetrahedron
Acknowledgement
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[
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Sui, Tetrahedron: Asymmetry 1999, 10, 3319–3325.
We thank the State Key Project of Basic Research (Project 973) (No.
G2000048007), Shanghai Municipal Committee of Science and Technolo-
gy, Chinese Academy of Sciences (KGCX2-210-01), and the National
Natural Science Foundation of China for financial support (20025206,
2
03900502, and 20272069).
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ꢀ 2004 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
5515