Catalytic oxidation of alcohols using molecular oxygen mediated by poly(ethylene glycol)-supported nitroxyl radicals |
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| Affiliation: | 1. School of Chemistry, The University of Reading, P.O. Box 224, Whiteknights, Reading RG6 6AD, UK;2. A.H. Marks and Company Ltd., Wyke, Bradford BD12 9EJ, UK;1. College of Chemistry and Chemical Engineering, Xinyang Normal University, Xinyang 464000, PR China;2. Henan Key Laboratory of Utilization of Non-metallic Mineral in the South of Henan, Xinyang 464000, PR China;1. The Key Laboratory of Food Colloids and Biotechnology, Ministry of Education, School of Chemical and Material Engineering, Jiangnan University, Wuxi, Jiangsu, 214122, China;2. Southern College (huai''an) of Nanjing Forestry University, Jiangsu, 223003, China;1. College of Chemistry and Environmental Science, Qujing Normal University, Qujing 655011, Yunnan, China;2. College of Chemical Engineering and Material, Quanzhou Normal University, Quanzhou 362000, Fujian, China;1. Key Laboratory of Design and Assembly of Functional Nanostructures, Fujian Provincial Key Laboratory of Nanomaterials, Fujian Institute of Research on the Structure of Matter, Chinese Academy of Sciences, YangQiao West Road 155#, Fuzhou, 350002, PR China;2. College of Materials Science and Engineering, Fuzhou University, Fuzhou, Fujian, 350108, PR China |
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| Abstract: | The selective catalytic oxidation of alcohols over a mixture of copper(I) chloride and a number of linear ‘linker-less’ or ‘branched’ poly(ethylene glycol)-supported nitroxyl radicals of the 2,2,6,6-tetramethyl-piperidine-1-oxyl (TEMPO) family as a catalyst system has been investigated in the presence of molecular oxygen in a batch reactor. It is found that the activity profile of the polymer-supported nitroxyl radicals is in good agreement with that of low-molecular weight nitroxyl catalysts, for example, allylic and benzylic alcohols are oxidised faster than aliphatic alcohols. The oxidations can be tuned to be highly selective such that aldehydes are the only oxidation products observed in the oxidation of primary alcohols and the oxidations of secondary alcohols yield the corresponding ketones. A strong structural effect of the polymeric nitroxyl species on catalytic activity that is dependent upon their spatial orientation of the nitroxyl radicals is particularly noted. The new soluble macromolecular catalysts can be recovered readily from the reaction mixture by solvent precipitation and filtration. In addition, the recycled catalysts demonstrate a similar selectivity with only a small decrease in activity compared to the fresh catalyst even after five repetitive cycles. |
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