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Enantioselective Conjugate Addition of Dialkylzinc and Diphenylzinc to Enones Catalyzed by a Chiral Copper( I ) Binaphthylthiophosphoramide or Binaphthylselenophosphoramide Ligand System
Author(s) -
Shi Min,
Wang ChunJiang,
Zhang Wen
Publication year - 2004
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.200400254
Subject(s) - enantioselective synthesis , chemistry , ligand (biochemistry) , conjugate , chiral ligand , denticity , stereochemistry , catalysis , medicinal chemistry , copper , combinatorial chemistry , organic chemistry , metal , mathematical analysis , biochemistry , receptor , mathematics
The enantioselective conjugate addition of dialkylzinc or diphenylzinc to enones was catalyzed by a copper( I )‐axially chiral binaphthylthiophosphoramide or binaphthylselenophosphoramide ligand system at room temperature (20 °C) or 0 °C, affording the Michael adducts in high yields with excellent ee for cyclic and acyclic enones. The enantioselectivity and reaction rate achieved here are one of the best results yet for the Cu‐catalyzed conjugate addition to enones. It was revealed that this series of chiral phosphoramides was a novel type of S,N‐bidentate ligands on the basis of 31 P NMR and 13 C NMR spectroscopic investigations. The mechanism of this asymmetric conjugate addition system has been investigated as well. We found that the acidic proton of phosphoramide in these chiral ligands play a significant role in the formation of the active species. A bimetallic catalytic process has been proposed on the basis of previous literature. The linear effect of product ee and ligand ee further revealed that the active species is a monomeric Cu I complex bearing a single ligand [Cu I :ligand 1:1].