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

摘要

The chiral sulfonamide-thiophosphoramide ligand LI,prepared from the reaction of(1R,2R)-(-)-l,2-cyclohexanediamine with diphenylthiophos-phoryl chloride and p-toluenesulfonyl chloride,was used as a chiral ligand in Cu(MeCN)_4ClO_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-biden-tate ligands on the basis of ~1H NMR,~31P NMR and ~13C 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.