Cerium-Catalyzed C-H Functionalizations of Alkanes Utilizing Alcohols as Hydrogen Atom Transfer Agents
Cerium-Catalyzed C-H Functionalizations of Alkanes Utilizing Alcohols as Hydrogen Atom Transfer Agents
复制标题
利用醇作为氢原子转移剂的铈催化烷烃 C-H 官能化
DOI：
10.1021/jacs.0c00212
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发表时间：
2020-04-01
影响因子：
15
通讯作者：
Zuo, Zhiwei
中科院分区：
文献类型：
--
作者：
An, Qing;Wang, Ziyu;Zuo, Zhiwei
现代光氧化还原催化传统上依赖于金属-配体电荷转移(MLCT)对金属多吡啶配合物的激发来利用光能活化有机底物。在这里，我们展示了利用丰富而廉价的三氯化铈作为催化剂，用配体到金属电荷转移(LMCT)激发的Ce醇盐络合物催化烷烃活化的应用。从Ce催化的C-H胺化反应和碳氢化合物的烷基化反应中可以看出，这一反应流形使得大量的醇类能够通过具有高能量挑战的烷氧基直接进入，作为实用的和选择性的氢原子转移(HAT)试剂。此外，通过一系列光谱实验研究了LMCT激发事件，揭示了一个快速的键均解过程和有效的烷氧基产生，共同排除了LMCT/均解事件是这种C-H官能化的速率决定步骤。
Modern photoredox catalysis has traditionally relied upon metal-to-ligand charge-transfer (MLCT) excitation of metal polypyridyl complexes for the utilization of light energy for the activation of organic substrates. Here, we demonstrate the catalytic application of ligand-to-metal charge-transfer (LMCT) excitation of cerium alkoxide complexes for the facile activation of alkanes utilizing abundant and inexpensive cerium trichloride as the catalyst. As demonstrated by cerium-catalyzed C-H amination and the alkylation of hydrocarbons, this reaction manifold has enabled the facile use of abundant alcohols as practical and selective hydrogen atom transfer (HAT) agents via the direct access of energetically challenging alkoxy radicals. Furthermore, the LMCT excitation event has been investigated through a series of spectroscopic experiments, revealing a rapid bond homolysis process and an effective production of alkoxy radicals, collectively ruling out the LMCT/homolysis event as the rate-determining step of this C-H functionalization.