Nitro reductive ring fission

Details of the mechanism have revealed the role of Meisenheimer-type hydride complexes, which is consistent with the presence of the strongly electron-withdrawing nitro groups that facilitate what are formally hydride reductions involving reduced coenzyme F420 (Ebert et al. 1999). For example, 2,4,6-trinitrophenol is reduced successively by hydride transfers catalyzed by F420, followed by loss of nitrite, further reduction, and ring fission to 4,6-dinitrohexanoate (Hofmann et al. 2004). 

Methylamiuomethylindole. The reaction of 2-methyl-5-nitroisoquinolinium iodide (1) with TiCla (7.7 equiv.) gives 4-methylaminomethylindole (2) directly in 20% yield. The conversion proceeds via reduction of the nitro group to an amino group, ring fission, and recyclization. 

The triazole forms by combination of ring-fission products with hydrazine. Similar reactions of hydrazine with 2-nitroimidazoles in the presence of palladium-carbon result in reduction of the nitro group <84JOC932>, while 1-methylbenzimidazole-3-oxide gives 2-hydrazino-l-methylbenzimidazole... 

Sulfonation of nitroso compounds by sodium hydrogen sulfite leads to amino sulfonic acids by simultaneous reduction.1240 194 When aromatic nitro compounds are subjected to this reaction, sulfonation in the ring is accompanied by formation of arylamine-JV-sulfonic acids (arylsulfamic acids), which on acid fission also give amino sulfonic acids this reaction, known in the literature as the Piria reaction, has been reviewed in papers by Hunter and his co-workers.195... 

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