N. M. Dobaeva

Cation-radical oxidation step in the nitration of phenothiazine with nitric acid

A phenothiazine cation radical, which was isolated preparatively in the form of the perchlorate in the reaction of phenothiazine with the minimum amount of nitric acid in aqueous perchloric acid, is formed initially in the nitration of phenothiazine with nitric acid to give 3-nitrophenothiazine S-oxide. The perchlorate is also converted to the nitro compound by nitration. During nitration the phenothiazine cation radical is oxidized to the phenazthioniuin cation, the perchlorate of which was also isolated preparatively in the reaction of phenothiazine with HNO3 in amounts that were twice the amount required for the formation of the phenothiazine cation radical. This is followed by the formation of the nitro derivative, which involves the reaction of the phenazthionium cation with the nitrite anion of nitrous acid. The resulting 3-nitrophenothiazine is then converted to the final product.