Asymmetric aldol reaction of enol trichloroacetate catalyzed by tin methoxide and BINAP·silver(I) complex

Enol trichloroacetate of cyclohexanone has been found to react with benzaldehyde in the presence of a catalytic amount of tributyltin methoxide and stoichiometric amount of MeOH to give an aldol adduct. Methanolysis of the in situ generating tin alkoxide of aldol adduct regenerates the tin methoxide, and thus the aldol reaction can proceed catalytically. The use of BINAP·silver(I) complex as an additional catalyst results in formation of optically active aldol products. This catalytic method has been further applied to the asymmetric reaction of diketene with benzaldehyde.