Azo bond hydrogenation with hydrazine, R–NHNH2, and hydrazobenzene

Hydrogenation of azo bonds with hydrazine, mono-substituted hydrazine, and hydrazobenzene was studied with selected diazene compounds under oxygen-free conditions. The reactions proceed rapidly and in high yield in several solvents, utilizing all N–H protons. While the reduction process is accompanied by the evolution of nitrogen gas in the case of N2H4, the intermediacy of diimide could not be confirmed by standard trapping experiments.