Research on nitrogen containing heterocyclic compounds. XVIII. Synthesis of 9H-pyrrolo[2,1-c]-s-triazolo[4,3-a][1,4]benzodiazepine,a novel tetracyclic ring of pharmaceutical interest

Reaction of di-4-morpholinylphosphinic chloride on 5,10-dihydro-9H-pyrrolo2,1-c]1,4]benzodiazepin-11-one 9 afforded 11-(di-4-morpholinylphosphinyloxy)-5H-pyrrolo2,1-c]1,4]benzodiazepine 10 . Displacement of di-4-morpholinylphosphinyloxy group of 10 by formylhydrazine with concomitant intramolecular cyclization led directly to 9H-pyrrolo2,1-c]-s-triazolo4,3-a]1,4]benzodiazepine 7, a novel nitrogen heterocyclic ring of pharmaceutical interest. A new procedure for the synthesis of 9 is also described.