Several pyrido[2,1-b]thiazines and thiazolo[2,3-a]pyridines were synthesized by reactions of cinnamonitriles with appropriate halocarbonyl compounds. Hydrazones of 3-diazotized aminopyrazolo[3,4-b]pyridinones were synthesized by coupling of their corresponding diazonium salts with several active methylene reagents. The obtained hydrazones were cyclized in refluxing ethanol containing a catalytic amount of triethylamine to afford the corresponding pyrazolopyridotriazines. All structures were established by considering the data of elemental analyses, IR, 1H-NMR, and mass spectra.
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Attaby et al. (1998) studied this question.