Asymmetric Syntheses of γ-Butyrolactones and Cyclobutanones

Significance

Organocatalytic asymmetric syntheses of γ-butyrolactones and cyclobutanones have been developed. Benzylidenecyclopropanes 1 react with oxone (3.2 equiv) in the presence of chiral ketone 2 (20 mol%) to provide γ-butyrolactones 3 in reasonable yields and good enantioselectivities. The transformation presumably proceeds via an asymmetric epoxidation followed by a ring expansion and a Baeyer-Villiger oxidation. Using more catalyst 2 (70 mol%) and less oxone (0.7 equiv) results in the formation of cyclobuta­nones 4 in moderate yields and high enantioselectivities.