The diastereoselectivity of electrophilic attack on trigonal carbon adjacent to a stereogenic centre: diastereoselective aldol reactions of open-chain enolates having a stereogenic centre carrying a silyl group at the ? position

Trigonal electrophiles react with lithium enolates having β-silyl groups 2, or with the corresponding silyl enol ethers 7, with high diastereoselectivity in the sense 1, to give largely the anti products 3. Aldehydes react with the same lithium enolates 2, and the analogues 10, with high diastereoselectivity, not only in the sense 1, but also with high diastereoselectivity for the formation of anti aldols 11 from the E-enolates and syn aldols 12 from the Z-enolates. Three adjacent stereogenic centres are set up in one operation, with easy control over the aldol geometry, because of the ease with which the enolate geometry can be controlled.