Novel Cu(Ⅰ)/TEMPO/NMI Catalytic Systems And Their Selective Catalytic Oxidation Of Alcohols

Selective oxidation of alcohols to the corresponding aldehydes（ketones）is a type of organic chemical reaction of great importance.Traditionally,the oxidation of alcohols is achieved by using stoichiometric amount of strong oxidants such as chromium salts,high-valence iodine reagents and peroxides.However,there are a serial of shortcomings for those apporaches,for example,poor atomic economy,safety hazard,high cost,harmful by-products and serious environmental pollutions.Therefore,it is essential to develop green,mild reaction conditions,efficient and economic catalytic systems for the oixdation.In this dissertation,selective catalytic oxidation of alcohols under mild reaction conditions was investigated using Cu（I）/TEMPO/NMI as the catalysts and air as the oxidant,which was devoted to following three sections.Section Ⅰ:Cu X/TEMPO/NMI（X=Cl,Br,I,NMI=1-Methylimidazole,TEMPO=2,2,6,6-Tetramethyl-1-piperidinyloxy）homogeneous catalytic systemsAmong the three cuprous halides,the iodide generally demonstrates the highest activity,for example,in the oxidation of 1-octanol at ambient temperature under 24 hrs’reaction.However,in the aerobic oxidation of benzylic alcohols,the chloride showed superiority to the iodide in that the aerobic oxidation was quantitatively completed within 3 h at ambient temperature whereas the iodide showed only about half the activity of the chloride analogue under the same conditions.By using electrochemistry,electric conductivity,and ¹H NMR titration,it was revealed that the surprising anomaly was due to the difference in the rate of forming active species,[Cu（NMI）₂X（Me CN）],from the polymeric solid in a two-stage process.Substrate expansion of 11 benzylic alcohols indicated that Cu Cl/NMI/TEMPO system converted quantitatively benzylic alcohols into corresponding aldehydes within 3 hrs’reaction and showed great tolerance to the substituents on the phenyl ring of the substrates.Section Ⅱ:Cu₂S/TEMPO/NMI heterogeneous catalyst systemWith Cu₂S as the chief catalyst and TEMPO and NMI as co-catalysts,benzyl alcohol could be efficiently oxidized to corresponding benzyl aldehyde under optimal conditions.Up to five repetitive runs,the activity of the catalyst showed no significant decrease.Characterisation with XRD,Raman,NMR and other technologies showed that the catalyst（Cu₂S）remained structurally unchanged,indications of the stability of the catalyst.A possible catalytic mechanism was also proposed.Section Ⅲ:SnO₂-Cu₂O/TEMPO/NMI heterogeneous catalyst systemThe composite oxide SnO₂-Cu₂O was prepared by deposition-precipitation method,and the synergistic interaction between the two metal oxides and its influence on the catalytic performance towards the aerobic oxidation of benzyl alcohol.The catalytic reaction conditions were optimized and its catalysis on the aerobic oxidation of benzyl alcohol was preliminarily explored.Its recyclability was also examined.