Efficient Copper-Catalyzed Ullmann Reaction of Aryl Bromides with Imidazoles in Water Promoted by a pH-Responsive Ligand.

A series of 1,10-phenanthroline derivatives were used as supporting ligands for copper-catalyzed Ullmann reaction in neat water. The catalytic system based on 4,7-dihydroxy-1,10-phenanthroline has demonstrated the promising catalytic performances for aryl bromides. The catalytic system was applicable to a wide scope of substrates, high catalytic activity and selectivity were observed for the reactions of electron-deficient, electron-rich, and heterocyclic aryl bromides with imidazoles containing different steric hindrance. The superior promoting effect of 4,7-dihydroxy-1,10-phenanthroline is attributed to its water solubility under the basic conditions. [ABSTRACT FROM AUTHOR]