Aromatic nitro compounds photoreduction

The photoreduction of aromatic nitro compounds to the amino compounds can be carried out on the surface of semiconductor particles such as titanium oxide1 with H-atom donors (equation 1). At a shorter duration of the photoinduced reduction of p-nitroacetophenone, the hydroxylamine intermediate can be obtained in about 30% yield. The reaction mechanism proposed is based on the photoexcitation of TiC>2 to generate an electron and a positive hole (equations 2 and 3). Aliphatic nitro compounds such as 12-nitrododecanoic acid can be reduced to 12-amino dodecanoic acid in 90% yield by this method. 

Selective reduction of a halogenated aromatic nitro compound to the corresponding hydroxylamine or amine upon irradiation of Ti02 suspended in degassed alcohol has also been reported, as has the selective photoreduction of / -nitrobenzaldehyde to the corresponding aldehydic aniline (Eq. 30) [170], and alkyl azides can also be reduced to the corresponding amine. 

An excellent review was given by Frolov, Kuznetsov and Hltsov [52] on the photoreduction of aromatic nitro compounds through intermolecular action. Alcohols and hydrochloric acid supply the hydrogen needed for reduction alcohols are converted into aldehydes, as in reaction (1) and hydrochloric acid... 

Modest amounts, of formamides and/or ureas resulted from reaction of aliphatic and cycloalkyl nitro compounds with Fe(CO)s (Alper, 1972b). Photoreduction of aromatic nitro compounds to nitroso compounds or... 

Photoreduction of aromatic and aliphatic nitro compounds gives hydroxylamines or amines, which is well reviewed.125 The radical reaction of primary nitro compounds with tin hydride does not give the denitrated product (see Chapter 7), but give the corresponding oximes (Eq. 

A different mode of reaction, however, is observed in photoreductions of nitroaromatics by aromatic tertiary amines. Irradiation of benzene solutions of N-methylated anilines and either m-chloronitrobenzene or 1-nitronaphthalene results in oxidative demethylation of the amines accompanied with reduction of the nitro compound to the corresponding arylamine 49). The authors suggest that hydrogen abstraction from the methyl group takes place as the primary chemical event. 

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