Copper-catalyzed intramolecular N-arylation of ureas in water: a novel entry to benzoimidazolones

The copper-catalyzed intramolecular N-arylation of 2-bromoarylureas performed in water leading to the benzo[d]imidazolone framework is reported. The scope of the methodology presented herein proved to be broad and afforded a significant number of benzoimidazolones in good to excellent yields. The reported protocol is based on the use of CuI and TMEDA acting both as the ligand and as the base in a water solution, which allows for the easy separation of the catalyst containing aqueous phase from the products by simple extraction. Additionally, the N- versus O-arylation competitive processes are also discussed.