Reactive intermediates. Part XIII. Benzocyclopropenones as intermediates in the oxidation of 3-aminobenzotriazin-4-ones

Oxidation of 3-aminobenzotriazin-4-ones with lead tetra-acetate proceeds by two simultaneous independent routes, which involve (a) the loss of one mol. of nitrogen to form indazolones and (b) the loss of two mol. of nitrogen to form benzocyclopropenones. The indazolones, which can be intercepted by dienes, react with nucleophiles without rearrangement of the carbonyl group. Benzocyclopropenones react with nucleophiles with rearrangement of the carbonyl group to give isomeric pairs of benzoic acid derivatives. Concerted fragmentations of intermediate aminonitrenes are proposed to explain these results. The mechanisms suggested are supported by an 15N-labelling experiment and by extended Huckel molecular orbital calculations.