Derivatives of pyrido[2,3-b][1,4]diazepine and of the dipyrido[1,2-a : 2 ',3 '-d]imidazole heterocyclic system [1]

With a continuing interest in hetepopolycyclic systems which may show biolo gical activities, we studied the reaction of 3-amino-2-(methylamino)pyridin e with diethyl 1,3-acetonedicarboxylate in order to develop pyridodiazepino ne derivatives. From the reaction mixture, we separated dipyrido[1,2-a:2',3 '-d]imidazole derivatives (3 and 4) besides two isomeric pyrido[2,3-b][1,4] diazepine derivatives (5 and 6) in which the complex structural differentia tion was achieved through nmr experiments and chemical evidence. Several at tempts to elaborate isomers 5 and 6 have not yet given significant results.