Mechanistic Studies on the Photocatalytic Reduction of Nitroaromatic Compounds

Heterogeneous photocatalysis is widely used in a broad variety of chemical reactions such as oxidations, dehydrogenation and hydrogen transfer. The photocatalyzed reduction of nitro groups has been used to prepare organic compounds with important industrial and biological applications. The formation of the desired compound could be controlled by selecting the adequate reaction conditions such as catalyst and solvent. This review presents a broad overview of the reaction mechanisms in photocatalytic reduction of nitrobenzene to develop a viable route to produce a sole or major product through high chemo- and regio-selectivity under mild conditions. The aniline, azo and azoxy formation is discussed according to catalyst selection, and also solvent effect has been examined. Finally, examples of synthesis of organic compounds via photocatalytic reduction of nitro compounds even in the presence of reducible groups such as carbonyl, cyano, alkyne and alkene are presented. Keywords: Photocatalytic reduction, nitroaromatic compounds, aniline, azobenzene, selectivity, mechanistic studies.