1,2,3-Triazole and Its Analogues: New Surrogates for Diazo Compounds

Abstract

Readily accessible and shelf-stable 1,2,3-triazole and its analogues such as pyridotriazole, triazoloindole, benzotriazole, and thiadiazole exist in equilibrium with their ring-opened isomers, viz., diazo compounds. These ring-opened isomers could be trapped by various metal catalysts (e.g., Rh, Pd, Cu, Co, Ag, etc.) to generate the corresponding metal carbenoids with extrusion of nitrogen. As a consequence, these unique N-heterocycles facilitate access to a realm of N-containing complex structural motifs of biological importance through denitrogenative transformations such as transannulations, insertions, ylide formation, and rearrangements by trapping of the metal carbenoids with a diverse range of coupling partners (e.g., alkenes, alkynes, nitriles, carbo/heterocycles, X–H/C–X bonds, etc.). Hence, suitably substituted triazole derivatives have emerged as efficient surrogates of diazo compounds for the generation of reactive metal carbenoids during the past decades. In this comprehensive review, we aim to discuss in detail the remarkable advancement in their synthesis and synthetic applications.

Reactivity of quinone methides with carbenes generated from α-diazocarbonyl compounds and related compounds

“…Anbarasan's group reported the synthesis of benzopyran compounds from in situ generated α-imino rhodium carbenes and o -QM intermediates via the rhodium-catalyzed denitrogenative transannulation of N -sulfonyl-1,2,3-triazoles with ortho -hydroxy benzhydryl alcohols. 35 N -Sulfonyl-1,2,3-triazole derivatives 122 are the precursors of α-diazoimines 36 via ring–chain isomerism, in the presence of a rhodium catalyst (Rh 2 (Oct) 4 ), to form α-imino rhodium carbenes 125 (Scheme 21a). The nucleophilic attack of the carbonyl group of o -QM 126 onto the electrophilic α-imino rhodium carbene 125 then generates the carbonyl ylide 127 (Scheme 21a).…”

Advances in Selected Heterocyclization Methods

“…Further developments of metalloradical chemistry toward heterocycle synthesis has been extensively reported and updated. 8c 5 32…”

“…Further developments of metalloradical chemistry toward heterocycle synthesis has been extensively reported and updated. 8c, 5,32 Scheme 11 Visible-light-induced palladium-catalyzed generation of aryl radicals from aryl triflates toward oxindoles and isoindolin-1-ones…”

Natural Product-Oriented Photo-Induced Denitrogenative Annulations of 1-Alkenylbenzotriazoles

“…1,2,3-Benzotriazoles are an important class of heterocycles that have found widespread applications in organic synthesis, medicinal chemistry, and material science [ 9 , 10 , 11 , 12 , 13 ]. Historically, it has been reported that some 1-substituted 1,2,3-benzotriazoles could undergo denitrogenative transformations to generate other valuable products.…”