Asymmetric 1,4-Addition of Diethylzinc to Cyclic Enones Catalyzed by Cu(I)-Chiral Sulfonamide-Thiophosphoramide Ligands and Lithium Salts

Abstract

The chiral sulfonamide-thiophosphoramide ligand L1, prepared from the reaction of (1R,2R)-(-)-1,2-cyclohexanediamine with diphenylthiophosphoryl chloride and p-toluenesulfonyl chloride, was used as a chiral ligand in Cu(MeCN) 4 ClO 4 -promoted catalytic asymmetric addition of diethylzinc to cyclic enones using LiCl as an additive in which up to 90% ee can be realized under mild conditions within 0.5 h. This chiral ligand is stable and recoverable after usual work-up and can be reused in the same catalytic asymmetric reaction. Moreover, it was found that this series of chiral ligands represents a type of S,O-bidentate ligands on the basis of 1 H NMR, 3 1 P NMR and 1 3 C NMR spectroscopic investigations. The linear effect of ligand ee and product ee further revealed that the active species is a monomeric Cu(I) complex bearing a single ligand.