Nitro-compounds reduction

Acknowledgement is made to the Natural Sciences and Engineering Research Council of Canada for support of theoretical work on the problem of variation of a with T which is, in part, reported in this chapter. The author is also grateful to professors J. O M. Bockris, E. Gileadi and M. Weaver, and Dr. J. Appleby, to whom this chapter was circulated prior to publication, for their comments. Thanks are due also to Professor E. B. Yeager for provision of data on O2 reduction in phosphoric acid and for material related to Eq. (24) in this chapter to Dr. R. P. Bell, F.R.S., for helpful discussion in correspondence on the question of temperature dependence of Brpnsted coefficients to Professor D. F. Evans for provision of unpublished data on nitro-compound reduction and to Messrs. D. F. Tessier and D. Wilkinson in our laboratory for helpful discussion on various points. 

Dr. Fred Guengerich at Vanderbilt University has published mechanistic schemata for cytochrome P450 involvement in an extensive array of both common and uncommon oxidative reactions and reductive reactions. Some of those are exhibited later in this chapter in a brief consideration of reductive reactions. Mechanisms for carbon hydroxylation, heteroatom oxygenation, N-dealkylation, O-dealkylation, alcohol oxidation, arene epoxidation, phenol formation, oxidation of olefins and acetylenes, reduction of nitro compounds, reductive dehalogenation, and azo reduction, to name a few, are provided. 

Amino groups can often be placed on a benzene ring by reduction of the corresponding nitro compound. Reduction of nitro compounds is a key step in what is probably the most important synthetic route in aromatic chemistry. The nitro compounds can be reduced in two general ways (1) by catalytic hydrogenation using molecular hydrogen or (2) by chemical reduction, usually by a metal and acid. The two methods of reduction can be illustrated as follows ... 

Nitroso compounds as a reaction intermediate for nitro compound reductions were investigated as substrates for mechanism understanding by Cenini and his colleagues [18]. The isolation of a paramagnetic complex suggested that the first step of the interaction between Pd(0) and the nitroso species is an electron transfer reaction. The palladium carbomethoxy complex from the reaction of a palla-dium(O) complex with PhNO under CO pressure in methanol was also isolated, which fits with the published reaction mechanism [19]. 

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