Nickel-catalysed direct C2-arylation of N-heterocyclic carbenes

A highly efficient nickel catalysed method for the direct C2-arylation of N-heterocyclic carbenes (NHCs) is reported. This protocol enables a facile access to C2-arylated imidazolium salts (NHC–Ar)X (X = Cl, Br, I or OTf). Experimental and theoretical studies suggest the viability of a Ni(I)/Ni(II) catalytic pathway in which the dinuclear Ni(I) species [(NHC)NiX]2 plays a key role.