Oxidation of nitroso compounds

Nitroso compounds are oxidized to nitro compounds by hydrogen peroxide or its derivatives and also by potassium dichromate (equation 485) [655]. 

The oxidation of 3-nitroso-2,6-diaminopyridine with 30% hydrogen peroxide at 35 °C for 1.5 h furnishes 3-nitro-2,6-diaminopyridine in 96% yield [278], Under these conditions, the primary amino groups are not affected. Nitrosoamines are oxidized with peroxytrifluoroacetic acid to nitroamines in 73-95% yields (equation 486) [291]. 

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The reaction of phenols with nitrous acid gives the ortho- and para-nitroso products, which are formed through a neutral dienone intermediate, the proton loss from the latter being the rate-limiting step" " . It has been shown that the nitrous acid can act as a catalyst for the formation of the nitro derivatives. Thus the conventional preparation of nitro compounds by the oxidation of nitroso compounds may be replaced by methods using an electron-transfer pathway in certain cases. In the latter method, the phenoxide reacts with nitrosonium ion to give the phenoxy radical and nitric oxide radical. The nitric oxide radical is in equilibrium with the nitronium radical by reaction with nitronium ion. The reaction of the phenoxy radical with the nitroninm radical resnlts in the formation of the ortho- and para-mixo prodncts" . Leis and coworkers carried ont kinetic stndies on the reaction of phenolate ions with alkyl nitrites and fonnd that the initially formed product is the 0-nitrite ester, which evolves by a complex mechanism to give the ortho-and the para-nitro products". ... 

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