Rhodium-Catalyzed Asymmetric Synthesis of Difluoro-β-lactams

Abstract

A novel approach to the synthesis of chiral difluoro-β-lactams is accomplished by an enantioselective Rh-catalyzed Reformatsky-type reaction. Nucleophilic (-)-menthyl difluoroacetyl zinc derivatives react with imines and spontaneous removal of the menthyl auxiliary occurs to give the chiral lactams in moderate yields and good enantioselectivities. The steric bulk of the imine affects the yield but not the enantioselectivity of the reaction. Aliphatic imines afforded lower yields and enantioselectivities compared to aryl imines.