N-Aryl-2-nitrosoanilines as intermediates in the synthesis of substituted phenazines from nitroarenes

N-Aryl-2-nitrosoanilines, available from the reaction of nitroarenes with anilide anions, undergo cyclization to furnish substituted phenazines. The reaction is promoted by potassium carbonate in methanol, N,O-bis(trimethylsilyl)acetamide (BSA) in aprotic solvents, and by acetic acid. The method is illustrated by the synthesis of 1-methoxyphenazine, a precursor of pyocyanine, starting from the appropriate nitroarene-aniline pairs.