Synthesis, Characterization, and Antiviral Activities of Pyridopyrazolotriazines

A pyrazolo[3,4-b]pyridine-5-carbonitrile derivative was diazotized to give the corresponding diazonium salt, which was used as a good synthon to synthesize pyrido[2′,3′:3,4]pyrazolo[5,1-c]triazines via its coupling with several active hydrogen-containing reagents, e.g., 2,4-pentandione, ethyl 3-oxo-butanoate, diethylmalonate, malononitrile, 2-cyanoethanethioamide, and ethyl cyanoacetate. Also, it reacted with phenylisothiocyanate to afford the corresponding pyrazolo[3,4-b]pyridin-3-ylphenylthiourea derivative, which, in turn, was used for further chemical transformations. The data of IR, 1 H NMR, mass spectra, and chemical analyses elucidated the structures of all newly synthesized heterocyclic compounds. Cytotoxicity, anti–HSV1 and anti–HAV, and MBB activities were evaluated for all newly synthesized heterocyclic compounds.