Oxidative N—N-coupling of aminopyridines with electrochemically generated NaOCl as the convenient method for the synthesis of substituted azodipyridines

Tendencies for reactions of aminopyridines with NaOCl generated electrochemically both in aqueous solution and in the heterophase H₂O—Bu^tOH system were estimated for the first time. Aminopyridines readily soluble under conditions of single-step process reacted with NaOCl in aqueous solution to give azodipyridines in high yields (up to 83%). The reaction efficiency depended on the position of NH₂ group at the pyridine ring and decreased upon going from 3- to 2- and 4-aminopyridines. A two-step synthesis of azodipyridines in the yield of up to 85% was proposed for aminopyridines poorly soluble in water, which was carried out under mild conditions in the H₂O—Bu^tOH system. It was also found that the reaction of 2-aminopyridine with either NaOBr or NiO(OH) generated electrochemically does not give azodipyridines.