N‐Heterocyclic Carbene Catalyzed γ‐Dihalomethylenation of Enals by Single‐Electron Transfer

Abstract An N‐heterocyclic carbene (NHC) catalyzed dihalomethylenation of enals is described. It is a rare example of merging NHC catalysis with single‐electron chemistry, a challenging topic with limited previous success. The versatile carbon‐centered trihalomethyl radicals have been demonstrated, for the first time, to be compatible with an NHC‐bound intermediate, thus leading to efficient and regioselective intermolecular C−C bond formation. The mild process provides straightforward access to unsaturated δ,δ‐dihalo esters.