Synthesis and biological screening of some novel 6-substituted 2-alkylpyridazin-3(2H)-ones as anti-inflammatory and analgesic agents.

Some novel derivatives of 2-alkyl 6-substituted pyridazin-3(2H)-ones were synthesized by condensation of 3,6-dichloropyridazine with the sodium salt of benzyl cyanide, followed by hydrolysis and coupling with alkyl halides. The synthesized compounds were screened as cyclooxygenase (COX)-1/COX-2 inhibitors and as analgesic and anti-inflammatory agents. Among the synthesized compounds, 6-benzyl-2-methylpyridazin-3(2H)-one (4a), 6-benzoyl-2-propylpyridazin-3(2H)-one (8b), and 6-(hydroxy(phenyl)methyl)-2-methylpyridazin-3(2H)-one (9a) displayed the highest COX-2 selectivity indices of 96, 99, and 98, respectively, and analgesic efficacies of 47%, 46%, and 45% protection, respectively. Also, compounds 4a, 8b, and 9a showed anti-inflammatory activities of 65%, 60%, and 62% inhibition of edema, respectively, at a dose of 10 mg/kg, which is higher than that of diclofenac (58% inhibition of edema).