Oxidovanadium(IV) sulfate catalyses light-driven C–N bond formation

Oxidovanadium(IV) sulfate, V^IVOSO₄, is shown to catalyze efficiently the amidation of the C–H bond of aldehydes by N-chloramine derivatives for the selective synthesis of amides. The catalytic process is driven by visible light irradiation at room temperature, and the reaction is carried out in ethyl acetate, a green and bio-based solvent. The catalyst, as an inorganic salt of an earth-abundant transition metal, is easily available, stable and inexpensive and is superior compared to other tested transition metal salts and complexes. The proposed reaction mechanism is obtained through the use of a combination of experimental and computational techniques. EPR spectroscopy suggests an interaction of the amine with the V^IVO²⁺ ion and the formation of V^IV/V^V and radical organic intermediates. Density functional theory (DFT) unveils a light-induced radical mechanism via an unusual V^IVOCl(SO₄) complex. The mechanistic proposal opens perspectives for the extended application of vanadium salts toward highly desirable dechlorination processes as well as for harsh C–H activations.