THE PHOTOCYCLIZATION OF N-ACYL-2-NITRODIPHENYLAMINES TO PHENAZINE N-OXIDES - SCOPE AND MECHANISM

The photocyclization of N-acyl-2-nitrodiphenylamines to phenazine N-oxides is extended to several dinitro derivatives and a pyridine analogue obtaining N-oxides of otherwise difficult access. In the presence of some additives, the reaction takes a different course. Thus, with acids deacylation occurs, with triphenylphosphine a N-phosphoranylidene amine is formed and with 2,6-di-ter-butylphenol the corresponding nitrosodiphenylammine is obtained. A mechanism starting from the nitroamide triplet and involving several discrete intermediates is proposed in order to account for such observations.