Gold-catalyzed cyclization of allene-substituted malonate esters: synthesis of beta,gamma-unsaturated delta-lactones.

An efficient method for the preparation of beta,gamma-unsaturated delta-lactones has been developed. The starting materials for the synthesis of these compounds are allene-substituted malonates which undergo gold-catalyzed cyclization by means of nucleophilic attack of the ester moiety on the allene. It is worth mentioning that this is the first example where an ester group attacks as a nucleophile in a gold-catalyzed transformation of allenes.