CuAAC is a simple reaction with good chemical selectivity and almost no by-products. Therefore, CuAAC has become the most popular research field in click chemistry.
First, the monovalent copper ion ligand is inserted into the terminal alkyne to generate the alkynyl-copper complex (a) with high reaction activity. Then, the electrophilic terminal N in the azide group attacks the nucleophilic C in the copper alkynyl compound to form a C-N bond, forming a copper hetero six-membered ring (b) which is rearranged and transformed into the most critical intermediate 5-triazolyl copper (c). Finally, the 1,4-substituted triazole product (d) is produced by protonation. (Figure 1)[1]
