Ring-expanded N-heterocyclic carbenes for copper-mediated azide-alkyne Click cycloaddition reactions

A series of well-defined copper(I) complexes bearing ring expanded N-heterocyclic carbene (NHC) ligands has been applied to the azide-alkyne cycloaddition reaction. The obtained results notably showed that the six membered NHC ligands outperform well-established five-membered ones. [CuI(Mes-6)] displayed a remarkable catalytic activity while respecting the strict criteria for Click reactions