Synthesis and reaction of α-oxo ketene dithioacetals

Abstract

$\alpha$-Oxo ketene dithioacetals were prepared from $\beta$-keto esters, carbon disulfide and alkyl halide in the presence of potassium carbonate. $\alpha$-Pyrones were synthesized from $\alpha$-oxo ketene dithioacetals and arylaldehydes or ketone using sodium hydride as base. The decarboxylation of $\alpha$-pyrones gave divinyl ketones with evolution of carbon dioxide. $\alpha$-Oxo ketene dithioacetals were reduced with magnesium in methanol and subsequently decarboxylated in the presence of methane sulfonic acid to give the half-protected 1,3-dicarbonyl compounds.