New copper(II) species from the copper/2,2′-bypyridine and copper/4-dimethylaminopyridine catalyzed aerobic alcohol oxidations

It is known that both Cu/BPY/TEMPO and Cu/DMAP/TEMPO are efficient catalyst systems for the aerobic oxidations of alcohols (BPY: 2,2′-bipyridine; DMAP: 4-dimethylaminopyridine; TEMPO: 2,2,6,6-tetramethylpiperidinyl-1-oxyl), the reactivity difference between the two systems and relevant copper species involved in the catalysis are, however, scarcely investigated. In this work, we attempted to isolate and characterize new possible CuII species participating in the catalytic reactions, and compared the catalytic aerobic oxidation of benzylic alcohol in the presence of both catalyst systems under similar conditions. In addition to the isolation of a new ionic complex from the Cu/DMAP/TEMPO reaction system in CH2Cl2–MeOH, a dinuclear CuII complex different from all previously reported species is observed from a separate experiment while performed in CH3CN. Another structurally related dinuclear CuII complex of BPY is also isolated from the Cu/BPY/TEMPO mediated reaction. The catalytic reactivity of both in-situ formed catalysts and isolated CuII complexes is tested towards the aerobic oxidation of benzylic alcohol.

Three new Cu(II) species resulting from the Cu/BPY/TEMPO and Cu/DMAP/TEMPO catalytic reactions were isolated and structurally characterized. The catalytic reactivity of the relevant catalyst systems for the aerobic oxidation of benzylic alcohol was compared.Figure optionsDownload as PowerPoint slide