Chapter 11 - Reduction of Nitro, Nitroso, Azo and Azoxy Groups

Abstract

Reduction of nitrocompounds involves a series of one-electron additions and chemical steps, and an important reaction intermediate is the nitrosocompound. Nitrosobenzene radical-anion is detected in a steady-state concentration during the electrolysis of a solution of the nitrosobenzene in acetonitrile within the cavity of the esr spectrometer. Both the radical-anion and the protonated radical are present, and protonation occurs at nitrogen generating nitroxide. Immediately following the generation by pulse-radiolysis, nitrosobenzene radical-anion is detected by absorption spectroscopy with λmax 450 nm. The reduction of aliphatic nitrocompounds in acid solution proceeds in two steps. The nitrosocompound is formed. A low steady state concentration of 2-methyl-2-nitrosopropane is detected during the reduction of 2-methyl-2-nitropropane. Good yields of the hydroxylamine are obtained from nitroalkanes with no α-hydrogen substituent by reduction in the acid solution. This step is used to modify the antibiotic everninomicin, a naturally occurring aliphatic nitrocompound, where the hydroxylamine is obtained by reduction at pH 8 in the presence of other functional groups.