Strategies for the Synthesis of [1,2,4]Triazolo[1,5-a]pyridine-8-carbonitriles

Abstract

Conjugated heterocyclic compounds with a 1,2,4-triazole core are of scientific interest due to their wide application in both synthetic and medicinal chemistry. In this review, we comprehensively summarize the synthetic methods for [1,2,4]triazolo[1,5-a]pyridine-8-carbonitriles. The methods are classified as follows: convertion of 8-substituted [1,2,4]triazolo[1,5-a]pyridines; synthesis based on functionalized pyridines, containing a nitrile group; synthesis based on heterocyclization of 2-(1,2,4-triazol-5-yl)acetonitriles, including cyclocondensation of 2-(1,2,4-triazol-5-yl)acetonitriles with β-dicarbonyl compounds and heterocyclization of 2-(1,2,4-triazol-5-yl)acetonitriles with α,β-unsaturated nitriles and esters; cyclocondensation of acyclic reagents, namely hydrazine derivatives and substituted methylenemalononitriles or their precursors and recyclization of oxadiazolopyridi-nium salts upon the interaction with ammonia or amine.