γ-Methylidene-δ-valerolactones: New Reagents for Palladium-Catalyzed Intermolecular Cyclization Reactions

Abstract

Abstract New reagents, γ-methylidene-δ-valerolactones, have been developed for the synthesis of various cyclic organic compounds under palladium catalysis, and a full overview of the use of these reagents have been described. These reagents primarily act as precursors for 1,4-zwitterionic species through oxidative addition to palladium(0) followed by decarboxylation, thereby introducing a four-carbon unit in a newly formed cyclic framework. In some cases, they can also be used for the synthesis of ring-expanded lactones as well as spirocyclopropane derivatives, depending on the substituents and/or the reaction conditions. Some mechanistic aspects of the newly developed catalysis have also been discussed.