Efficient catalysis of Ullmann-type arylation reactions by a novel trinuclear copper(I) complex with a chelating tricarbene ligand

A novel trinuclear copper(I) complex with a chelating tricarbene ligand is shown to be an efficient catalyst for the arylation of different classes of compounds containing N-H or O-H functions. Different kinds of azole rings (pyrazole, imidazole, 1,2,4-triazole) can be arylated with comparable efficiencies at relatively mild temperatures (100 °C). The catalyst activates aryl iodides, bromides and even chlorides for the reaction. An unusually strong influence of the nature of the aryl substituent on the reaction yield is observed. The synthetic protocol can be extended to other substrate classes, such as phenols and amides, although the catalytic efficiency with amides is significantly reduced.