A Cation-Directed Enantioselective Sulfur-Mediated Michael/Mannich Three-Component Domino Reaction involving Chalcones as Michael Acceptors

A new
approach has been developed for an asymmetric sulfur-mediated
three-component intermolecular Michael/Mannich domino reaction using
chalcones as Michael acceptors. This reaction is catalyzed by chiral
quaternary ammonium salts derived from modified quinine and provides
facile access to complex sulfur-containing compounds with three contiguous
stereogenic centers in yields of up to 93%, with 95:5 dr and 95% ee. These compounds were further elaborated
to give the equivalent of a chiral aza-Morita–Baylis–Hillman
reaction involving chalcones and azetidines bearing four chiral centers.