Generation of Donor/Donor Copper Carbenes through Copper‐Catalyzed Cycloisomerization/Oxidation of Vinyl‐Allenes: Constructing Functionalized Cyclopentenones

Transition-metal-catalyzed cycloisomerization of vinyl-allenes has attracted enormous attention over the past decades, and multitudinous efficient synthetic strategies have been discovered based on this methodology. However, the generation of metal carbenes in these reactions is mostly limited to the noble-metal catalysts (Au and Pt). Here we show that non-noble-metal catalyst (Cu) enable the catalytic cycloisomerization/oxidation of vinyl-allenes by generating α-alkyl alkenylcopper carbenes. This protocol leads to the practical and controllable construction of various valuable cyclopentenones in mostly good to excellent yields.