Behavior of 5,6-dihydrobenzo[h]cinnolinones towards hydrazine. Synthesis of benzo[h]cinnolinones and of 4-aminobenzo[h]cinnolinones

Dehydrogenation and amination of 4,4a,5,6-tetrahydro and 5,6- dihydrobenzocinnolinones in refluxing hydrazine hydrate to give new benzo[h]cinnolinones and 4-aminobenzo[h]cinnolinones are reported, and reaction mechanisms proposed. Experiments were also extended to 4,4a-dihydro- 5H-indenopyridazinone which underwent hydrazine induced dehydrogenation to 5H-indenopyridazin-3-one but not subsequent amination.