Hemiaminals as substrates for sulfur ylides: direct asymmetric syntheses of functionalised pyrrolidines and piperidines

Phenyl stabilised chiral sulfur ylides react with five-membered-ring hemiaminals to give functionalised pyrrolidines directly with high enantioselectivity. The reaction can be diverted to give piperidines instead by isolation of the intermediate epoxide and treatment with TMSOTf.