Pyridinyl-triazole ligand systems for highly efficient CuI-catalyzed azide-alkyne cycloaddition

Abstract

Pyridinyl-triazole ligand systems (including N2-2-pyridinyl 1,2,3-triazoles and N1/N2-substituted 2-(NH-1,2,3-triazol-4-yl)pyridines) were found to be superior ligands for CuI-catalyzed azide-alkyne cycloaddition (CuAAC) reactions. Low catalyst loadings, short reaction times, facile catalyst recyclability, ambient temperature, and open-flask conditions made this catalytic system very practical. The iodide anions could form iodine bridges to construct stable dinuclear Cu(I) complexes with these ligands, which was the key to achieve high catalytic activities. While CuBr and CuCl were not suitable for this ligand system because of the improper size of Br and Cl atoms for the formation of the corresponding dinuclear Cu(I) complexes.