Asymmetric Morita−Baylis−Hillman Reactions Catalyzed by Chiral Brønsted Acids

Abstract
Chiral BINOL-derived Brønsted acids catalyze the enantioselective asymmetric Morita−Baylis−Hillman (MBH) reaction of cyclohexenone with aldehydes. The asymmetric MBH reaction requires 2−20 mol % of the chiral Brønsted acid 2e or 2f and triethylphosphine as the nucleophilic promoter. The reaction products are obtained in good yields (39−88%) and high enantioselectivities (67−96% ee). The Brønsted-acid-catalyzed reaction is the first example of a highly enantioselective asymmetric MBH reaction of cyclohexenone with aldehydes.