Catalytic oxidation of hydrazo derivatives promoted by a TiCl ₃/HBr system

Through a novel catalytic process of general synthetic interest, hydrazo compounds were efficiently and selectively converted into corresponding azo derivatives. The proposed mechanism of this process comprises two separate and distinctive catalytic cycles, linked together by radical species. The first cycle includes formation of a hydroxy radical, generated by Ti(III) single-electron reduction of H₂O₂. In the second cycle, the hydroxy radical oxidizes HBr into hypobromous acid, which in turn is reduced back to HBr and water by a hydrazo substrate.