Abstract: Triplet-sensitized irradiation of the previously reported [4+ 21 photoadduct between naphthalene and N-methyltriazolinedione gave a di-7-methane rearranged urazole. The urazole was converted into diazabenzosemibullvalene by hydrazinolysis and oxidation. Solution thermolysis of the azo compound produced only small amounts of naphthalene, naphthvalene, benzofulvene, and mainly intractable material. Gas-phase pyrolysis gave ...