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.

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

N-Heterocyclic compounds like 1,2,3-triazoles serve as a key scaffolds among organic compounds having diverse applications in the field of drug discovery, bioconjugation, material science, liquid crystals, pharmaceutical chemistry and solid phase organic synthesis. Various drugs containing 1,2,3-triazole ring which are commonly available in market includes Rufinamide, Cefatrizine, Tazobactam etc., Stability to acidic/basic hydrolysis along with significant dipole moment support triazole moiety for appreciable participation in hydrogen bonding and dipole-dipole interactions with biological targets. Huisgen 1,3-dipolar azide-alkyne cycloaddition culminate into a mixture of 1,4 and 1,5- disubstituted 1,2,3-triazoles. In 2001, Sharpless and Meldal came across with a copper(I) catalyzed regioselective synthesis of 1,4-disubstituted 1,2,3-triazoles by cycloaddition between azides and terminal alkynes. This azide-alkyne cycloaddition has been labelled as a one of the important key click reaction. Click synthesis describes chemical reactions that are simple to perform, gives high selectivity, wide in scope, fast reaction rate and high yields. Click reactions are not single specific reaction, but serve as a pathway for construction of simple to complex molecules from a variety of starting materials. In the last few decades, 1,2,3-triazoles attracted attention of researchers all over the world because of their broad spectrum of biological activities. Keeping in view the biological importance of 1,2,3-triazole, in this review we focus on the various synthetic routes for the syntheisis of 1,4-disubstituted 1,2,3-triazoles. This review involves various synthetic protocols which involves copper and non-copper catalysts, different solvents as well as substrates. It will boost synthetic chemists to explore new pathway for the development of newer biologically active 1,2,3-triazoles.

Synthetic Routes for 1,4-disubstituted 1,2,3-triazoles: A Review

N-sulfonyl triazole is an intermediate in organic synthesis and has been proven to be an excellent nitrogen source for the construction of many heterocycles. Due to its more favorable pharmacokinetic properties, tetrazole has also been proven to be a suitable bioisostere derived from a carboxylic acid and cisamide units. This chapter summarizes the new and innovative synthetic strategies that have been developed for the synthesis and ring-opening of N-sulfonyl triazoles and tetrazoles. This chapter covers the chemistry of N-sulfonyl triazole and tetrazole and their applications in medicine and pharmaceuticals. Initially, we discussed various synthetic methods of N-sulfonyl-1,2,3-triazoles, and then how reactive N-sulfonyltriazole is sufficient to open the ring and form acyclic amine derivatives (β-phenethylamine, o-diamine, allylamine, enamine, and Ketimine) or other cyclic N-sulfonylamines. This chapter also introduces the synthesis and use of N-sulfonyl-1,2,3,4-tetrazole. We focused on the synthetic development for the production of N-sulfonyl triazole and tetrazole and their reaction types. 

Synthesis, chemistry and uses of N-sulfonated N-triazoles and N-tetrazoles

Efficient synthesis of 1-arylsulfonyl-1,2,3-triazoles from easily available (Z)-arylvinyl bromides is described. The sequential reaction involves elimination of HBr from (Z)-arylvinyl bromides promoted by KOH and copper-catalyzed (3+2) cycloaddition reaction between the alkyne intermediates and sulfonyl azides.

Wenjing Xu

Papers

Synthesis of 1-arylsulfonyl-1,2,3-triazoles from (Z)-arylvinyl bromides by sequential elimination–cycloaddition reaction

Synthesis of 1‐Arylsulfonyl‐1,2,3‐triazoles from (Z)‐Arylvinyl Bromides by Sequential Elimination—Cycloaddition Reaction.