Trimethylsilyl trifluoromethanesulfonate-catalyzed aldol reaction of various aldehydes with silyl enol ethers.

The aldol reaction of trimethylsilyl enol ethers (1-3) with various aldehydes in the presence of a catalytic amount of trimethylsilyl trifluoromethanesulfonate was investigated. With benzaldehyde (4) the β-hydroxycarbonyl compounds were obtained in good yields. The effect of a substituent on the benzene ring was also examined. Aliphatic aldehydes (11, 13, and 14) were found not to be suitable substrates for this catalytic aldol reaction. On treatment with tert-butyldimethylsilyl enol ethers (30 and 31) under the same conditions, benzaldehydes (4, 5, 7, 8) yielded the corresponding aldol products with good threo-selectivity.