Synthesis of Some Novel Pyridazine, Thienopyridazine, Pyrazolopyridine, Pyridopyrazolopyrimidine and Pyridopyrazolotriazine Derivatives with Their Antimicrobial Activity

Coupling of compound 1 with diazotized aromatic amines in ethanol afforded the arylhydrazones 3a,b. Fusion of 3a,b with active methylene derivatives 4a,b afforded the pyridazine derivatives 6a–d. Also, when compounds 6b,c were reacted with elemental sulphur afforded the thienopyridazine derivatives 7a,b. Treatment of compound 8 with hydrazine hydrate produced pyrazolopyridine derivative 9. Pyridopyrazolopyrimidines (12–19) and pyridopyrazolotriazines 21, 22a,b were achieved by the reaction of pyrazolopyridine with different reagents in basic media. The antimicrobial activities of the new compounds were also evaluated. The newly synthesized compounds were characterized by IR, 1 H NMR and 13 C-NMR spectral studies.