Rearrangement studies on acylketene O-prop-2-ynyl S-methylmonothioketals

Abstract

Acylketene O-prop-2-ynyl S-methylmonothioketals 3a–e, easily obtained through displacement on β-oxosulfonium salts 2a–e by prop-2-ynol, are shown to undergo facile rearrangement under neutral (toluene-xylene) and basic conditions (K₂CO₃-EtCOMe) to afford the diene esters 5a–e and the substituted furans 4a–e, respectively. The probable mechanism for the formation of the various products involving initial Claisen rearrangement of compounds 3a–e has been described.