Nickel-Catalyzed 4+2 Cycloaddition of Enones with Alkynes

摘要

A nickel-catalyzed 4 + 2 cycloaddition reaction has been developed where enones react with alkynes to afford polysubstituted pyrans. A mechanistic rationale is proposed, implying oxa-nickela cycle formation by oxidative cyclization of nickel to enone, followed by alkyne insertion.