Utility of Cyano Acid Hydrazide in Heterocyclic Chemistry: A New Route for the Synthesis of New l,2,4-Triazolo[l,5-a]pyridines and l,2,4-Triazolo[l,5-a]isoquinolines

Cyano acid hydrazide 1 was condensed with cyclohexanone in refluxing ethanolic piperidine to yield the hydrazone 4. Com pound 4 reacts with arylidines 5 a i to yield the 1,2,4triazolo[l,5-a]pyrid ines 7 a -i. C om pound 4 also reacts with m ixtures o f aliphatic aldehydes and different active m ethylene reagents to yield l,2 .4-triazolo[l,5-a]pyrid ines 8 a -d . Similarly reaction o f 4 with arylazom alononitrile to yield the triazolopyridines lO a-d. R eaction o f 4 with arom atic aldehydes gives 12a-e. C om pound 8a reacts with elem ental sulfur to yield the th ieno-l,2 ,4-triazolopyridine 13. This underwent cycloaddition with acrylonitrile, a»-nitrostyrene. chalcone, N -phenylm alem ide, dim ethylacetylenedicarboxylate and tetracyanoethylene yielding the isoquinolines 15-18. A ll new com pounds have been characterized by their IR, 'H N M R and mass spectra.