Catalytic Asymmetric Staudinger Reactions to Form β-Lactams:  An Unanticipated Dependence of Diastereoselectivity on the Choice of the Nitrogen Substituent

There are relatively few methods for the catalytic asymmetric synthesis of beta-lactams, and those that have been reported are generally cis selective. This communication describes the first catalytic enantioselective Staudinger reactions that preferentially furnish trans beta-lactams (trans = relationship of Ph to R1). The key to this method is the use of an N-triflyl protecting group for the imine. Along with serving as interesting targets in their own right, N-triflyl beta-lactams readily react with nucleophiles to generate useful families of compounds, such as gamma-amino alcohols and beta-amino acids.