Fused quinoline heterocycles VII: synthesis of new isoxazolo[3 ',4 ':4,5]pyrrolo(or thieno)[2,3-c]quinolines

3-Amino-4-chlorothieno(or pyrrolo)[3,2-c] quinoline-2-carboxylates 3a, b react with alkylamines 4a-g to give the corresponding 4-alkylaminothieno(or pyrrolo)[3,2-c]quinoline-2-carboxylates 5a-g. Diazotization of 5a-g, followed by reaction with NaN3, leads to the formation of 3-azido-4-alkylaminothieno(or pyrrolo)[3,2-c]quinoline-2-carboxylates 6a-g, a new heterocyclic ring system. Thermolysis of azido compounds 6a-g in bromobenzene at reflux temperature afforded the novel tetracyclic ring system isoxazolo[3',4':4,5]thieno[2,3-c]quinolines 7a-e and isoxazolo[3',4':4,5]pyrrolo[2,3-c]quinolines 7f,g.