Synthesis of butenolides from α-(phenylthio)-ketones and -esters: crystal structure of an intermediate β-phenylthio-γ-lacton

Abstract

Alkylation of α-(phenylthio)-ketones or -esters with iodoacetate anion gives 1,4-dicarbonyl compounds which are reduced stereoselectively to β-phenylthio-γ-butyrolactones. Oxidation to sulphoxides and thermolysis provides a general synthesis of β- and γ-substituted Δαβ-butenolides. Treatment of 5,5-dimethyl-4-oxo-3-(phenylthio)-hexanoic acid with NaBH4 gives a single γ-lactone whose PhS and But groups are shown to be cis by an X-ray crystal structure determination.