The effects of a remote stereogenic center in the Lewis base catalyzed aldol additions of chiral trichlorosilyl enolates.
Chiral trichlorosilyl enolates bearing a remote stereogenic center were employed in the phosphoramide-catalyzed aldol reaction. The additions of the methyl ketone enolates proceeded with only moderate diastereoselectivities. The addition of the Z-enolate to various aldehydes selectively produced the syn relative diastereomers. In both cases, the effect of the beta-silyloxy stereogenic center was modest, and the internal diastereoselection was mainly controlled by the catalyst. [reaction: see text]