Photobenzidine rearrangement: Photodecomposition of N.N'-dimethylhydrazoaromatics and 1,4-dialkyl-1,4-diphenyl-2-tetrazenes

Acid-catalyzed and thermal rearrangements of hydrazoaromatics have been well documented; however, little is known about light-2 induced benzidine rearrangements^ Weiss reported that azobenzene and aniline were formed in the photolysis of an alcoholic solution of hydrazobenzene with a mercury lamp. Later, traces of rearrangement product, ortho- and para-semidines, were detected in the reaction fixture by paper chromatography. Recently, Shine and co-workers found that N,N'-dimethyl- -aminodiphenylamine can be isolated as the major product of irradiation of,N'-dimethylhydrazobenzene in cyclohexane. Part of the present work is to explore the scope and the mechanism of photobenzidine rearrangements of some N,N'-d1methyldrazoaromatics. The acid-catalyzed reactions of some of these substrates are also carried out for comparison.