Asymmetric Aldol Reaction of Alkenyl Esters with α-Ketoesters Catalyzed by Chiral Tin Alkoxides

A catalytic enantioselective aldol reaction of alkenyl esters with α-ketoesters was achieved using an (R)-BINOL-derived chiral tin dibromide possessing a 4-t-butylphenyl group at 3- and 3’-positions as the chiral precatalyst in the presence of sodium methoxide and methanol. Optically active aldol products possessing a chiral tertiary carbon with up to 92% ee were diastereoselectively obtained in moderate to high yields not only from cyclic alkenyl esters but also from acyclic ones under the influence of the in situ generated chiral tin methoxide.