Copper salts reduction, aromatic nitro compounds

The nature of the azo bond is such that only a very limited number of possible functional groups can be considered to have the necessary features to serve as starting materials for reductive methods of preparation. In a sense, the Bogo-slovskii reaction [17, 18] may be considered a reduction of a diazonium salt by copper(I) ions. However, because the reaction resembles the other condensations of diazonium salts, its classification among the condensation reactions seems appropriate. The direct reduction of azoxy compounds as such is of minor preparative importance except as a method of identification of an azoxy compound. However, in the various bimolecular reduction procedures of aromatic nitro compounds, it has been postulated that an azoxy intermediate forms in the course of the reaction. This intermediate azoxy compound is ultimately reduced to an azo compound. 

Copper(II) salts in the presence of highly basic amines such as ethylenediamine and 3,3 -diaminopropylamine, catalyse the reduction of aliphatic and aromatic nitro compounds by CO/H2O at 85-90 °C and atmospheric pressure [83]. The CO2 that is evolved during the reaction is blocked by the amine and... 

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