Palladium-Catalyzed Regioselective [3 + 2] Annulation with N-Allenamides at the Proximal C═C Bond: Synthesis of γ-Amino-α′-methylenecyclopentenones

A palladium-catalyzed [3 + 2] cycloaddition of cyclopropenones with N-allenamides has been developed. This methodology facilitates the synthesis of γ-amino-α'-methylenecyclopentenones in moderate to excellent yields with good regioselectivity and compatibility with various functional groups. The employment of N-allenamides as versatile 2C synthons enables simultaneous incorporation of both a nitrogen atom and a methylene group into cyclopentenones. Furthermore, this approach exhibits reverse regioselectivity when compared to general allenes. Density functional theory calculations successfully elucidated the origin of the observed regioselectivity.