PYROLYSIS OF QUINOLINE-3,4-DICARBOXYLIC ANHYDRIDES BEARING 2-PHENYL, 2-BENZYL AND 2-ORTHO-TOLYL SUBSTITUENTS - FORMATION OF PRODUCTS OF CARBENE INSERTION AND ADDITION

Flash vacuum pyrolysis of 2-phenylquinoline-3,4-dicarboxylic anhydride at 800-degrees/0.06 mm gave indeno[1,2-b]indole (30-40%), which readily added nucleophiles Y- at C-10 to give 5,10-dihydro derivatives (Y = H, Me, Ph, NEt2, OMe, CH(COOMe)2 and CMe2NO2). Similar Pyrolysis of the 2-benzylquinoline anhydride gave a 1:2 mixture of the (expected) linear 5H-benzo[b]carbazole and the (unexpected) angular 7H-benzo[c]carbazole. The isomeric 2-o-tolylquinoline anhydride on similar pyrolysis gave mainly 11H-benzo[a]carbazole (85%), isomeric benzocarbazoles (4%) and 11H-indeno[1,2-b]quinoline (2.6%). Most of these products are probably derived from exocyclic carbenes formed by aryne - carbene equilibration, but the last compound may be formed by direct aryne - methyl interaction.