Practical and robust method for stereoselective preparations of ketene silyl (thio)acetal derivatives and NaOH-catalyzed crossed-Claisen condensation between ketene silyl acetals and methyl esters
NaHMDS–2TMSCl). The first catalytic NaOH-catalyzed crossed-Claisen condensation between ketenesilylacetals and methyl esters proceeded successfully to give a variety of α-monomethyl β-ketoesters and inaccessible α,α-disubstituted β-ketoesters. For further extension, a couple of Claisen-aldol tandem reactions of the obtained β-ketoester analogues utilizing TiCl4 and TiCl4–Bu3N reagents smoothly proceeded