Transition Metal-Catalyzed Coupling Reaction of meso-Cyclic Anhydrides with Allylic Zinc Reagent

Abstract

The enantioselective desymmetrization of meso-3,5-dimethylglutaric anhydride provides syn-deoxypolypropionate motif which is one of the ubiquitous structures within nature. We have envisioned to extend to vinylation or allylation of meso-3,5-dimethylglutaric anhydride with organozinc reagents, providing more useful syn-deoxypolypropionate synthons. Unexpectedly, the rhodium-catalyzed allylation of meso-3,5-dimethylglutaric anhydride with allylic zinc reagent provided the undesired allylic ester in moderate yield. This result suggests that the electrophilic allylating agent was generated in the catalytic system to afford the allylic ester. The generation of nucleophilic allylating agent was examined by employing monoallylzinc or diallylzinc reagents and a variety of electron-donating ligands (PHOX, BINAP, MonoPHOS). Lewis acids also were employed to increase the electrophilicity of carbon atom of carbonyl group. Although the organozinc reagent generally has been utilized as a nucleophile, allylic zinc reagents have functioned as an electrophile in our system.