Isomeric nitroaromatic

The isomerization of an arylamine to an N-containing aromatic heterocyclic compound would, in principle, open a new route from aromatic hydrocarbons, via nitroaromatic compounds and arylamines, to pyridines and quinolines. We were therefore interested to discover the potential of this reaction, and have studied its scope, optimum conditions, and its mechanism [8-11]. 

Other reductive transformations are sometimes involved in nitroaromatic degradation pathways. Pseudomonase pseudoalcalignes ]S S is able to grow on nitrobenzene as sole carbon source. Nitrobenzene is reduced, first to nitrosobenzene, and then to the hydroxylamine, which is isomerized via a mutase enzyme to 2-aminophenol, as shown in Figure 8. The remaining pathway then follows an oxidative meta-cleavage route. 

Scheme 6 exemplifies the first path. Intramolecular cyclization of sulfonamides 1 is caused by action of a base, thus resulting in the formation of nitroaromatics fused with five- or six-membered heterocycles [22-24]. It should be emphasized that in some cases the formation of isomeric products can be observed due to a nucleophilic attack at the para-position relative to the nitro group. Also it is worth noting that the cyclic sulfamides 2 and 3 can be used as precursors to obtain some other N-heterocyclic compounds, such as isoindoles 4 [25] or 1,2,3,4-tetrahydroquinolines 5 [24] (Scheme 6). 

In some cases one observes the addition of two molecules of nucleophile to the nitroaromatic, to form a 1 2 complex. A particularly interesting aspect of the 1 2 complexes is the possibility of detecting cis-trans isomerism. Such isomerism has in fact been observed in the addition of sulfite ion to... 

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