Abstract 2, 4, 6-Trimethylazobenzene has been shown to undergo photochemical cyclodehydrogenation in sulphuric acid to give 2, 4-dimethylbenzo [c] cinnoline and 1, 2, 4- trimethylbenzo [c] cinnoline. The formation of the former involves cyclization with the loss of a methyl substituent: the formation of the latter involves cyclization with the migration of a methyl substituent. The reaction involves a photochemical disproportionation: 4-(4- ...
