Aerobic Oxidative Ammination Of Alcohols To Nitriles Catalyzed By TEMPO-Cu-based Catalytic Systems

A TEMPO quaternary ammonium salt was synthesized, and the structures of this compound, as well as its intermediates in the synthesis it, were characterized by 1H-NMR,13C-NMR and HR-MS analysis. The TEMPO quaternary ammonium salt in combination with cuprous iodide and 2, 2-bipyridine as a catalytic system was applied to the aerobic oxidative ammination of primary alcohols to the corresponding nitriles with aqueous ammonia as nitrogen source. First the optimal the reaction conditions were obtained by using benzyl alcohol as a model substrate. After receiving the optimal reaction conditions,the catalytic system was applied to the aerobic oxidative amination of various alcohols,including benzylic, allylic alcohols as well as heteroatom-containing aromatic alcohols, to their corresponding nitriles. The results showed that all the above alcohols can be smoothly transformed to their corresponding nitriles in high selectivity and yields. Besides, the TEMPO quaternary ammonium salt can be recovered easily and reused for 5 times without significant loss of activity.The aforementioned catalytic system was applied to the aerobic oxidative ammination of primary alcohols to the corresponding nitriles in a deep eutectic solvent composed choline chloride and urea in a rate of 1:2. The effects of reaction temperature, copper source and the quantity of each component in the catalytic system including copper salt,2,2-bipyridine and the TEMPO quaternary ammonium salt were evaluated with benzyl alcohol as a model substrate. The catalytic system was applied to the aerobic oxidative ammination of various primary alcohols in the deep eutectic solvent mentioned above. The results show that primary benzylic alcohols, primary allylic alcohols and primary heteroatom-containing aromatic alcohols can be smoothly transformed to their corresponding nitriles in high selectivity and yields.