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.
The copper‐catalyzed reaction of α‐halo‐N‐tosylhydrazones with H‐phosphoryl compounds is reported to afford alkenylphosphoryl compounds in modest to good yields. The reaction may take place via a copper‐promoted Bamford‐Stevens‐type reaction of an α‐phosphorylated diazo intermediate. The diazo intermediate is trapped by an excess H‐phosphoryl compound to give α, N‐bisphosphoryl hydrazone in the absence of a copper catalyst.
The value of functional pyrrolidines in the fields of biology, pharmacology, catalysis and natural product synthesis stimulates an intensive interest in developing new synthetic methods for this class of compounds, and direct functionalization of the simple pyrrolidine represents an attractive and effective approach. Herein, we report a metal-free protocol for direct N-arylation and α-functionalization of pyrrolidine via redox-neutral three-component reactions in which p-quinol ethers or p-quinone monoacetals serve as the arylation components and the formal oxidants for α-functionalization of pyrrolidine.
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