Photochemical iron-catalyzed decarboxylative azidation via the merger of ligand-to-metal charge transfer and radical ligand transfer catalysis
Photochemical iron-catalyzed decarboxylative azidation via the merger of ligand-to-metal charge transfer and radical ligand transfer catalysis
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DOI：
10.1016/j.checat.2023.100603
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发表时间：
2023-06-15
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影响因子：
--
通讯作者：
West, Julian G.
中科院分区：
文献类型：
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作者：
Kao, Shih-Chieh;Bian, Kang-Jie;West, Julian G.
使用化学计量的铜盐的配体-金属电荷转移（LMCT）最近已显示允许通过LMCT/自由基-极性交叉（RPC）机制形成脱羧C-N键;然而，该方法不能起催化作用并且不能成功地接合未活化的烷基羧酸，这对该方法的普遍适用性提出了挑战。利用LMCT和自由基-配体-转移（RLT）的概念，本文报道了第一个光化学的铁催化直接脱羧叠氮化反应。在叠氮基三甲基硅烷的存在下简单地照射廉价的硝酸铁催化剂允许各种各样的羧酸以宽的官能团耐受性和温和的条件直接转化为相应的有机叠氮化物。有趣的是，该反应进行不需要额外的外部氧化剂，简化了反应方案。最后，机理研究与自由基机理一致，并表明硝酸根抗衡阴离子作为铁催化剂周转的内氧化剂。
Ligand-to-metal charge transfer (LMCT) using stoichiometric copper salts has recently been shown to permit decarboxylative C-N bond formation via an LMCT/radical-polar crossover (RPC) mechanism; however, this method is unable to function catalytically and cannot successfully engage unactivated alkyl carboxylic acids, presenting challenges to the general applicability of this approach. Leveraging the concepts of LMCT and radical-ligand-transfer (RLT), we herein report the first photochemical, iron-catalyzed direct decarboxyla-tive azidation. Simply irradiating an inexpensive iron nitrate catalyst in the presence of azidotrimethylsilane allows for a diverse array of carboxylic acids to be converted to corresponding organic azides directly with broad functional group tolerance and mild conditions. Intriguingly, no additional external oxidant is required for this reac-tion to proceed, simplifying the reaction protocol. Finally, mecha-nistic studies are consistent with a radical mechanism and suggest that the nitrate counteranion serves as an internal oxidant for turnover of the iron catalyst.