On treatment with hydrazine hydrate (80%) and methylhydrazine, oxazolo [3, 2-b] pyridazinium perchlorates (I) furnish hemi-perchlorates of 4H-pyridazino [6, 1-c][1, 2, 4] triazines (VI) and 1-methyl-4H-pyridazino [6, 1-c][1, 2, 4] triazinium perchlorates (VIII), respectively. On reaction with phenylhydrazine by refluxing in acetonitrile, I affords an osazone (XII), a phenylazopyridazine (XIII) and its hydrazo derivative (XIV), which are also ...