Mediator-Enabled Electrocatalysis with Ligandless Copper for Anaerobic Chan-Lam Coupling Reactions.
Mediator-Enabled Electrocatalysis with Ligandless Copper for Anaerobic Chan-Lam Coupling Reactions.
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无配体铜介体电催化厌氧Chan-Lam偶联反应。
DOI：
10.1021/jacs.1c02103
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发表时间：
2021-04-28
影响因子：
15
通讯作者：
Sevov CS
中科院分区：
文献类型：
--
作者：
Walker BR;Manabe S;Brusoe AT;Sevov CS
简单的铜盐在一些合成中最常用的转化中作为催化剂来影响C-X键形成反应，包括芳基硼酸和胺的氧化偶联。然而，这些Chan-Lam偶联反应历来依赖于化学氧化剂，这限制了它们在小规模合成之外的适用性。尽管电化学在多种金属催化过程中成功地取代了强化学氧化剂，但无配体铜催化剂的电氧化反应受到电子转移动力学缓慢、不可逆镀铜和竞争性底物氧化的困扰。在此，我们报告了亚化学计量量的氧化还原介质的实施，以解决铜催化电合成的局限性。机理研究表明，介质具有多种作用，(i)快速氧化低价Cu中间体，（ii）从阴极剥离Cu金属以再生催化剂并显示活性Pt表面以进行质子还原，以及（iii）提供阳极过充电保护以防止底物氧化。该策略适用于在没有化学氧化剂的情况下芳基硼酸与芳基，杂芳基和烷基胺的Chan-Lam偶联。与空气中的常规反应相比，这些电化学条件下的耦合反应产率更高，反应时间更短，并提供互补的衬底反应性。
Simple copper salts serve as catalysts to effect C–X bond-forming reactions in some of the most utilized transformations in synthesis, including the oxidative coupling of aryl boronic acids and amines. However, these Chan–Lam coupling reactions have historically relied on chemical oxidants that limit their applicability beyond small-scale synthesis. Despite the success of replacing strong chemical oxidants with electrochemistry for a variety of metal-catalyzed processes, electrooxidative reactions with ligandless copper catalysts are plagued by slow electron-transfer kinetics, irreversible copper plating, and competitive substrate oxidation. Herein, we report the implementation of substoichiometric quantities of redox mediators to address limitations to Cu-catalyzed electrosynthesis. Mechanistic studies reveal that mediators serve multiple roles by (i) rapidly oxidizing low-valent Cu intermediates, (ii) stripping Cu metal from the cathode to regenerate the catalyst and reveal the active Pt surface for proton reduction, and (iii) providing anodic overcharge protection to prevent substrate oxidation. This strategy is applied to Chan–Lam coupling of aryl-, heteroaryl-, and alkylamines with arylboronic acids in the absence of chemical oxidants. Couplings under these electrochemical conditions occur with higher yields and shorter reaction times than conventional reactions in air and provide complementary substrate reactivity.
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影响因子：
18.3
作者：
Beatty, Joel W.;Stephenson, Corey R. J.
通讯作者：
Stephenson, Corey R. J.
影响因子：
15
作者：
Driver, MS;Hartwig, JF
通讯作者：
Hartwig, JF
影响因子：
16.6
作者：
D'Accriscio, Florian;Borja, Pilar;Nebra, Noel
通讯作者：
Nebra, Noel
影响因子：
62.1
作者：
Allen, Scott E.;Walvoord, Ryan R.;Padilla-Salinas, Rosaura;Kozlowski, Marisa C.
通讯作者：
Kozlowski, Marisa C.
影响因子：
18.3
作者：
Engle, Keary M.;Mei, Tian-Sheng;Wasa, Masayuki;Yu, Jin-Quan
通讯作者：
Yu, Jin-Quan