Progress on Pyridotriazole Chemistry: Synthesis and Transformations

Pyridotriazoles are an important subclass of azacyclic compounds. Although known in early 1950s, these compounds aroused little attention in synthetic chemistry for a long time. This situation has changed during the past years as ever-increasing recognitions on their rich properties and reactivities. Particularly, the recent exploration on their potentials as carbene or metal carbene precursors in denitrogenative transformations catalytically or non-catalytically has met considerable success. A lot of new synthetic approaches towards azacyclic compounds such as indolizines, imidazopyridines, pyridoisoquinolinones and pyridoindoles as well as a wide range of functionalized pyridines have been established based on the transformations of pyridotriazoles. Meanwhile, a considerable number of new reactions are developed for the synthesis of pyridotriazoles. In particular, the development of new transition-metal catalyzed tandem reactions has enabled selective generation of diverse pyridotriazoles in efficient manners from simple starting materials. This review surveys main advances in this field over the last two decades and aims to provide an up-to-date overview on the knowledge of pyridotriazole chemistry.