Reduction of Aromatic Nitro Compounds: The Fate of Arylhydroxylamines

Abstract

Electroreduction of aromatic nitro compounds in hydroxylic solvents is one of the oldest processes used in preparative electrolysis. Depending upon the electrode materials, geometry, reaction conditions and nature of the substrate used, numerous products have been isolated. The arylhydroxylamines are reactive species which can undergo both electroreduction to amine and electrooxidation to nitrosobenzene, in addition to numerous chemical reactions. The stabilization of the product of dehydration of the hydroxylamino derivative can also result from the presence of a ring nitrogen in some heterocyclic compounds. In five-membered heterocyclic rings the mutual position of the heteroatom and of the nitro group is of importance. Aromatic compounds, which bear in addition to the reducible nitro group a functional group that can undergo a condensation reaction with electrogenerated arylhydroxylamine, yield some unexpected products.