Catalytic oxidation of alcohols using molecular oxygen mediated by poly(ethylene glycol)-supported nitroxyl radicals
Catalytic oxidation of alcohols using molecular oxygen mediated by poly(ethylene glycol)-supported nitroxyl radicals
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DOI：
10.1016/j.apcatb.2005.05.006
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发表时间：
2005-11-09
影响因子：
22.1
通讯作者：
Tsang, SC
中科院分区：
文献类型：
--
作者：
Ferreira, P;Phillips, E;Tsang, SC
在间歇反应器中，研究了在分子氧存在下，在氯化铜和若干线性“无连接剂”或“支链”聚乙二醇负载的2,2,6,6-四甲基哌啶-1-氧（TEMPO）家族的硝基自由基的混合物上选择性催化氧化醇的反应。研究发现，聚合物负载的硝基自由基的活性谱与低分子量的硝基催化剂的活性谱一致，例如，烯丙醇和苯基醇比脂肪醇氧化得快。氧化可以调整为高度选择性，使得醛是在伯醇氧化中观察到的唯一氧化产物，而仲醇的氧化产生相应的酮。特别指出的是，聚合物硝基物种对催化活性的强烈结构效应取决于它们的硝基自由基的空间取向。通过溶剂沉淀和过滤，可以很容易地从反应混合物中回收新型可溶性大分子催化剂。此外，即使经过五次重复循环，再生催化剂也表现出与新鲜催化剂相似的选择性，活性仅略有下降。(c) 2005 Elsevier B.V.版权所有
The selective catalytic oxidation of alcohols over a mixture of copper(l) 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. (c) 2005 Elsevier B.V. All rights reserved.