Synthesis of substituted 1H-pyridazin-4-ones, 2-H-pyrazolo [4,3-c] pyridazines, pyrazoles and isoxazole derivatives

1-[4(2,4-Dioxo-pentane-3-yl) azophenyl]-2H-1,2,3-triazole (1) when treated with AcCl/ Ac2O in the presence of conc. H2SO4/PTSA gave N-acetylpentane-2,3,4-trione-3-[4-(2H-1,2,3-triazol-2-yl)] phenylhydrazone (2) and 3-acetyl-1 -(4-phenyl-2H-1,2,3-triazol-2-yl) 6-methyl-1 H-pyridazin-4-one (4). Compound (1) on treatment with NaH in THF followed by the addition of AcCl afforded N-acetyl derivative (2). 2 with NaH in THF rearranged to heptane-2,3,4,6-tetraone-3-[4-(2H-1,2,3-triazol-2-yl)] phenylhydrazone (3), which on heating yielded (4). On the other hand (4) was directly obtained by reacting (1) with AcCl/Ac2O in the presence of conc. H2SO4 or PTSA. The pyridazinone (4) was also obtained directly by prolonged reflux of (1) with AcCl in xylene. The pyridazinone (4) on treatment with N2H4, transformed to 2-[4-(2H-1,2,3-triazol-2-yl) phenyl] 3,7-dimethyl-2H-pyrazolo [4,3-c] pyridazine (5). The compound (1) on treatment with hydrazine or substituted hydrazines gave the corresponding substituted pyrazoles (6a-c) and (1) with hydroxylamine afforded corresponding substituted isoxazole (7).