Cu(bipy)2+/TEMPO-Catalyzed Oxidation of Alcohols: Radical or Nonradical Mechanism?
Cu(bipy)2+/TEMPO-Catalyzed Oxidation of Alcohols: Radical or Nonradical Mechanism?
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DOI：
10.1021/ic200725k
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发表时间：
2011-12-05
影响因子：
4.6
通讯作者：
Baerends, Evert Jan
中科院分区：
文献类型：
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作者：
Belanzoni, Paola;Michel, Carine;Baerends, Evert Jan
在用克里思作为催化剂的醇的氧化中，已经假设底物被氧化但未配位的克里思+（Semmelhack）或Cu配位的克里思中心点自由基（谢尔顿）。根据DFT计算，Cu（bipy）（2+）/克里思助催化剂体系的反应不是自由基反应，而是克里思+对醇C-H-α键的亲电攻击。该机理结合了Semmelhack机理（克里思氧化成克里思+）和谢尔顿提议（“在Cu的配位范围内”）的元素。最近的建议受到了挑战的DFT计算的基础上，不同的功能，据报道，导致一个自由基的机制。我们仔细检查的结果为两个泛函，并得出结论，从计算的能量和从电子结构分析，两个DFT泛函的结果是一致的，都导致与克里思不作为自由基，但作为（配位）正离子提出的机制。
In the oxidation of alcohols with TEMPO as catalyst, the substrate has alternatively been postulated to be oxidized but uncoordinated TEMPO+ (Semmelhack) or Cu-coordinated TEMPO center dot radical (Sheldon). The reaction with the Cu(bipy)(2+)/TEMPO cocatalyst system has recently been claimed, on the basis of DFT calculations, to not be a radical reaction but to be best viewed as electrophilic attack on the alcohol C-H-alpha, bond by coordinated TEMPO+. This mechanism combines elements of the Semmelhack mechanism (oxidation of TEMPO to TEMPO+) and the Sheldon proposal ("in the coordination sphere of Cu"). The recent proposal has been challenged on the basis of DFT calculations with a different functional, which were reported to lead to a radical mechanism. We carefully examine the results for the two functionals and conclude from both the calculated energetics and from an electronic structure analysis that the results of the two DFT functionals are consistent and that both lead to the proposed mechanism with TEMPO not acting as radical but as (coordinated) positive ion.