A Silyl Enol Ether Usable for Highly Stereoselective Aldol Reactions

Isopropenyloxytris(trimethylsilyl)silane (1) is a silyl enol ether substituted with three trimethylsilyl groups on a silicon atom. The tris(trimethylsilyl)silyl (TTMSS) group having a characteristic sterically hindered structure is called “super silyl group” and it contributes to highly diastereoselective synthetic reactions.^1-3) For example, when 1 is treated with 2-phenylpropanal in the presence of an acid catalyst, the reaction proceeds to obtain the adduct 2 as a nearly single diastereomer. Subsequent treatment with phenyl magnesium bromide affords the three-component adduct 3 with high anti-selectivity.¹⁾ In this way, 1 can give multi-component adducts with high diastereoselectivity by means of the sequential aldol reaction in one pot. Thus, 1 is effective for construction of highly stereo-controlled carbon chains.