Synthesis of Some New Pyridazine Derivatives for Anti-HAV Evaluation.

4-(2-(4-Halophenyl)hydrazinyl)-6-phenylpyridazin-3(2)-ones , were prepared and treated with phosphorus oxychloride, phosphorus pentasulphide and ethyl chloroformate to give the corresponding chloropyridazine, pyridazinethione, oxazolopyridazine derivatives -, respectively. Compound reacted with hydrazine hydrate to afford hydrazinylpyridazine . The reaction of 4-(2-(4-chlorophenyl)hydrazinyl)-3-hydrazinyl-6-phenylpyridazine () with acetic anhydride, -chlorobenzaldehyde and carbon disulphide gave the corresponding pyridazinotriazine derivatives -. On the other hand, 5-(4-chlorophenylamino)-7-(3,5-dimethoxybenzylidene)-3-phenyl-5-pyridazino[3,4-][1,4]thiazin-6(7)-one () was prepared directly from the reaction of compound with chloroacetic acid in presence of -chlorobenzaldehyde. Compound reacted with nitrogen nucleophiles (hydroxylamine hydrochloride, hydrazine hydrate) and active methylene group-containing reagents (malononitrile, ethyl cyanoacetate) to afford the corresponding fused compounds -, respectively. Pharmacological screening for antiviral activity against hepatitis A virus (HAV) was performed for the new compounds. 4-(4-Chlorophenylamino)-6-phenyl-1,2-dihydropyridazino[4,3-][1,2,4]triazine-3(4)-thione () showed the highest effect against HAV.