Enantioselective acylation of enolates; the reaction of (4R)-trans-diethyl 2-alkyl-2-methoxy-1,3-dioxolane-4,5-dicarboxylates with E- and Z-silyl enol ethers

Abstract

The stereoselectivity of the Lewis acid induced acylation of open-chain silyl enoi ethers by chiral orthoesters is strongly affected by the CC bond configuration: both Z and E silyl enol ethers are acylated in good isolated yields, but the Z isomers give rise to a 1 : 1 ratio of diastereoisomeric monoprotected 1,3-diketones, while excellent stereoselectivities are obtained with E enols.