Synthesis of δ-Bromo γ,δ-Unsaturated Carbonyl Compounds via Palladium-Catalyzed Bromoalkylation of Alkynoates

Palladium-catalyzed regio- and stereoselective intermolecular tandem reaction of electron-deficient alkynes, CuBr2, and allylic alcohol to synthesize delta-bromo-gamma,delta-unsaturated carbonyls was developed. A mechanism involving bromopalladation of alkyne, followed by insertion of allylic alcohol and allylic hydrogen shift, is proposed. The shift of allylic hydrogen is the rate-limiting step in this reaction.