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 β-lactams, and those that have been reported are generally cis selective. This communication describes the first catalytic enantioselective Staudinger reactions that preferentially furnish trans β-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 β-lactams readily react with nucleophiles to generate useful families of compounds, such as γ-amino alcohols and β-amino acids. Copyright © 2005 American Chemical Society.