Preparation of 2-Arylbenzoxazoles Catalyzed by Cu-Nanoparticles

Significance

A novel nano Cu catalyst was readily prepared from CuSO₄ and applied in the oxidative cyclization of Schiff bases forming a 2-arylbenzoxazole framework. Cu nanoparticles were prepared by mixing aqueous reverse micellar emulsions of CuSO₄ and N₂H₄ at 25 °C. The reaction mixture was extracted with absolute EtOH and the resulting nano Cu was rinsed with EtOH (removal of the surfactant molecules) to afford the nano Cu catalyst. The oxidative cyclization of Schiff bases was catalyzed by the nano Cu in MeOH in the presence of K₂CO₃ as a base under atmospheric molecular oxygen at 80-100 °C (eq. 1, 10 entries).