A PRACTICAL AND EFFICIENT METHOD FOR THE SYNTHESIS OF BETA-LACTONES

This paper describes a convenient one-step preparation of beta-lactones based on the addition of thiol ester enolates to carbonyl compounds. Under the proper conditions the resulting aldolates undergo spontaneous cyclization to produce beta-lactones in good to excellent yield. The new beta-lactone synthesis provides access to 2-oxetanones with a variety of substituents and substitution patterns. In general, thiol ester enolates combine with carbonyl compounds to form the less sterically crowded beta-lactone diastereomers, and in some cases the reaction proceeds with excellent stereoselectivity. In conjunction with the stereospecific decarboxylation of beta-lactones, this chemistry also provides a very attractive approach to the synthesis of substituted alkenes.