New Trends in Click Reactions for Synthesis of 1,2,3‐Triazole Derivatives

Among various heterocyclics, five-membered triazole nitrogen heterocycles show vast application in the medicinal, industrial, and agricultural sectors, and so forth. The Cu-catalyzed click reaction has gained significant attention from investigators for the selective synthesis of triazole derivatives, but the toxicity occurs due to excessive presence of copper in the final product and associated intake limits its application. In the quest for the development of sustainable synthetic strategies, copper-free, metal-free, and water-assisted reactions are becoming popular. In view of this, the present review article focuses on recent developments (last 10 years) made in sustainable click reactions to afford the synthesis of triazole derivatives in high yield, mild reaction conditions, easy isolation and purification of products from readily available starting materials. Besides, novel eco-friendly click reactions such as photocatalytic click reactions, water-assisted click reactions, metal-organic framework-based click reactions, metal-free click reactions, solvent-free click reactions, and electrochemical click reactions have been reviewed. In addition, various patents and current clinical trials on triazoles have been discussed.