Rhodium(III)-Catalyzed Activation and Functionalization of Pyridine C–H Bond by Exploring a Unique Double Role of “N-Heterocyclic Carbene–Pyridyl” Ligand Platform

A new rhodium­(III)-catalyzed protocol for C–H activation and functionalization of poorly reactive pyridine backbones with the aid of in-built N-heterocyclic carbene ligand has been presented. Mechanistic investigations including the isolation and single crystal X-ray structural characterization of the pre- and postfunctionalized rhodium­(III)-intermediates suggested a plausible pyridine-coordination effect in the present NHC-directed cyclometalative annulation of the C(3)–H bond of the pyridine rings with internal alkynes. The strategy enables us to overcome the challenges of functionalizing robust metal–CNHC backbone concomitant with pyridine C–H activation under an oxidizing environment.