Cyclisation and C-acylation of 2,6-dioxocyclohexylacetic acids

Abstract

The βγ-unsaturated γ-lactones, 2-hydroxy-6-oxocyclohex-1-enylacetic acid lactone and 2-hydroxy-4,4-dimethyl-6-oxocyclohex-1-enylacetic acid lactone undergo acylation on the carbon atom adjacent to the lactone carbonyl group on treatment with acetic anhydride in the presence of sodium acetate. The structures of these compounds were determined by nuclear magnetic resonance, ultraviolet and infrared spectroscopy, and by decarboxylation of the acylated gem-dimethyl compound to a known ketone. The βγ-unsaturated lactones were not isomerised to αβ-unsaturated lactones under a variety of reaction conditions.