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
Dialkyl trans-2-alkoxy-2-alkyl-1,3-dioxolan-4,5-dicarboxylates and the corresponding N,N,N,N-tetramethyl-4,5-diamides have been prepared respectively from dialkyl tartrates or tartaric acid diamides. They smoothly reacted with silylenolethers in the presence of Lewis acids to give enantiomerically enriched (up to 90% d.e.) monoprotected 1,3-diketones. A dramatic dependence of the stereochemical outcome from the configuration of the enolic double bond of 4 has been observed. The products can be stereoselectively reduced to give configurationally defined monoprotected 3-ketols.
HUDRLIK, P. F.;HUDRLIK, A. M.;KULKARNI, A. K., J. AMER. CHEM. SOC., 1985, 107, N 14, 4260-4264