Synthesis of Some New Heterocyclic Nitrogen Compounds Starting from Pyromellitic Dianhydride

Pyromellitic dianhydride 1 was used as starting compound for the synthesis of some new derivatives of condensed dipyrrole, dibenzoxazine, and dipyridazine. Thus, the diimide 2 was formed on fusion of 1 with urea, thiourea and/or thiosemicarbazide. Also, 1 reacted with benzylamine to give terephthalic acid derivative 3 which on fusion afforded the cyclic diimide 4. The reaction of 1 with o-aminothiophenol under different reaction conditions was investigated to give 5 in acetic acid or 6 in toluene and the later could be decarboxylated to 7. On the other hand, the action of AlCl 3 on 1 in presence of reactive aromatic substrates afforded the corresponding isomers 8a-d and 9a-d. which could be cyclized using hydroxylamine hydrochloride to give the dioxazine isomers 10a-d and 11a-d. The dioxazine isomers 10b and 11b were also obtained when 14 was allowed to react with AlCl 3 in anisol. Cyclization of 8a-d and/or 9a-d using hydrazine or phenylhydrazine gives the dipyridazine isomers 13a-h and/or 14a-f respectively.