What is the mechanism of click chemistry?

Click chemistry works by utilizing highly efficient chemical reactions that rapidly form new compounds from simple starting materials. A very common click reaction is the copper-catalyzed azide-alkyne cycloaddition (CuAAC) reaction. In this reaction, an azide functional group on one molecule reacts with an alkyne functional group on another molecule to form a triazole product. Initially, copper(I) ions interact with a ligand to form a copper complex. The alkyne functional group then undergoes oxidative addition with the copper(I) complex, resulting in the formation of a copper acetylide intermediate. Next, the azide functional group reacts with the copper acetylide intermediate through a 1,3-dipolar cycloaddition reaction, resulting in the formation of a triazole product. Sometimes a copper(II) species may form as a result of the reaction. This species can undergo reductive elimination to regenerate the copper(I) catalyst and release the triazole product.