Progress on Pyridotriazole Chemistry: Synthesis and Transformations

Abstract

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.

Visible Light-Induced Reactions of Diazo Compounds and Their Precursors

“…These heterocyclic compounds are robust, stable, and easily available . Recently, transition metal-catalyzed denitrogenative transformations of pyridotriazoles have emerged as a powerful tool for synthesis of diverse N -heterocyclic scaffolds. , These transformations take advantage of the ring–chain tautomerization of pyridotriazoles in solution into the corresponding diazo tautomer. Although the generation of carbene species from pyridotriazoles under photochemical conditions has been reported, it is important to note that these photolysis approaches involved the use of harmful, high-energy UVC irradiation, leading to many side reactions, thus limiting the synthetic applications of these methods .…”

Divergent cyclization of 2-(5-iodo-1,2,3-triazolyl)benzamides toward triazole-fused lactams and cyclic imidates

“…Fused 1,2,3-triazoles have gained high importance both as valuable scaffolds in medicinal chemistry 1 and as a stable “resting state” for the highly reactive diazoimines. 2 The discovery of catalytic approaches to 1,4- 3 and 1,5-disubstituted triazoles 4 rendered them as affordable and viable starting materials for the formation of fused triazoles. 5 Thus, the common route, utilizing the thermal intramolecular Huisgen cycloaddition 6 (Scheme 1A-1), was augmented by interrupted CuAAC combined with Ullmann-type C–C coupling (Scheme 1A-2) 7 or oxidative 8 capture (Scheme 1A-3).…”

New Carbene Donor for Biocatalysis: Stereodivergent Synthesis of Pyridyl Cyclopropanes via Enzymatic Activation of Pyridyltriazoles

“…39 Following pioneering reports on the use of 1,2,3-pyridotriazoles for rhodium-catalyzed Si-H insertion reactions, 40 these reagents have found utility in transannulations, insertions, ylide formation, and rearrangements for the synthesis of heterocycles. [41][42][43] More recently, 1,2,3-pyridotriazoles were also successfully employed for cyclopropanation reactions via in situ generation in combination with Co-porphyrin catalysts 39,44 or via light induced activation. 45 However, asymmetric variants of these reactions have so far remained elusive.…”