Synthesis and anti H₅N₁ activities of some novel fused heterocycles bearing pyrazolyl moiety

Ring transformation of the acid hydrazide, derived from 2(3H)-furanone, into triazolopyridazine, triazolothiadiazole, and triazolothiadiazine derivatives, was investigated. The structures of all synthesized compound were demonstrated on the basis of their analytical and spectral data. The antiviral effect of the synthesized compounds against the highly pathogenic avian influenza (HPAI H₅N₁) was evaluated.