Palladium(0)-Catalyzed Asymmetric Cycloaddition of Vinyloxiranes with Heterocumulenes Using Chiral Phosphine Ligands: An Effective Route to Highly Enantioselective Vinyloxazolidine Derivatives

摘要

Cycloaddition reaction of 2-vinyloxiranes with carbodiimides using Pd_2(dba)_3 .CHCl_3, and TolBINAP as the chiral ligand, in THF at ambient temperature, afforded 4-vinyl-1, 3-oxazolidin-2-imines in 70-99/100 yield and in up to 95/100 ee. The stereoselectivity is strongly influenced by the structure of the chiral phosphine ligands and substrates, as well as by the reaction conditions.