Enantioselective Synthesis of the Optically Active α-Methylene-β-hydroxy Esters, Equivalent Compounds to Morita−Baylis−Hillman Adducts, Using Successive Asymmetric Aldol Reaction and Oxidative Deselenization

[Chemical reaction: See text] The asymmetric aldol reaction of a tetra-substituted ketene silyl acetal including an alkylseleno group with aldehydes has been developed by the promotion of Sn(OTf)2 coordinated with a chiral diamine to afford the corresponding aldols having chiral quaternary centers at the alpha-positions. The facile oxidative deselenization of these aldol compounds produces optically active alpha-methylene-beta-hydroxy esters which correspond to adducts prepared by the asymmetric Morita-Baylis-Hillman reaction.