Nitro-aromatic compounds activation pathways

Fig. 10.2 Metabolic activation pathways leading to mutation in nitro-aromatic compounds. Ring-oxidation might occur in the ortho, meta, or para position. Shown in the figure is the para metabolic ring-oxidation. Figure adapted from [15]...

A reduction of nitro substituent, under both aerobic and anaerobic conditions, seems to be a common enzymatic mechanism in the environment [5,29]. Such reduction has been demonstrated in various organisms which utilize the nitro compotind as an electron acceptor. The activity of nitroreductases, many of which have a broad substrate specificity, has been demonstrated in cell-free systems, and some enzymes have been purified and characterized [5,19,29]. The resulting aromatic amines are often further transformed into persistent azo compounds or polymers by biotic or abiotic processes [1,30,31]. In the second pathway, the nitro substituent is directly removed as nitrite [24,32,33], with the formation of catechol. 

There has been a major review of substitution by the radical-chain 5rn1 mechanism. It has been shown that reaction by the SrnI pathway of the enolate anions of 2- and 3-acetyl-l-methylpyrrole may yield a-substituted acetylpyrroles. The dichotomy of reactions of halonitrobenzenes with nucleophiles has been nicely summarized major pathways include reduction via radical pathways and. SnAt substitution of halogen. EPR spectroscopy has been used to detect radical species produced in the reactions of some aromatic nitro compounds with nucleophiles however, whether these species are on the substitution pathway is questionable. The reaction of some 4-substimted N,N-dimethylanilines with secondary anilines occurs on activation by thallium triacetate to yield diphenylamine derivatives radical cation intermediates are proposed. ... 

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