Syntheses of rac- and optically active 2-alkyl-γ-butyrolactones and 2- alkyl-cyclobutanones

γ-Butyrolactones have been produced in good yield from alkylidene cyclopropanes, as racemates or as an enantiomerically enriched mixture of stereoisomers (e.e.>60%) depending upon the method used. Optically active cyclobutanones which are intermediate in the process have been in some cases isolated. We show the limitations of a competitive method previously described and point out its weak step.