Electroreductive Radical Borylation of Unactivated (Hetero)Aryl Chlorides Without Light by Using Cumulene-Based Redox Mediators.
Electroreductive Radical Borylation of Unactivated (Hetero)Aryl Chlorides Without Light by Using Cumulene-Based Redox Mediators.
复制标题
使用基于积烯的氧化还原介体，在无光的情况下对未活化的（杂）芳基氯进行电还原自由基硼化。
DOI：
10.1002/anie.202310246
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发表时间：
2023
期刊：
影响因子：
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通讯作者：
Milner,PhillipJ
中科院分区：
文献类型：
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作者：
Lai,Yihuan;Halder,Arjun;Kim,Jaehwan;Hicks,ThomasJ;Milner,PhillipJ
单电子转移（SET）在许多化学过程中起着关键作用，从有机合成到环境修复。然而，惰性底物（Ep/2<−2 V vs Fc/Fc+）的选择性还原，如普遍存在的电子中性和富电子（杂）芳基氯化物，仍然是一个主要的挑战。 目前的方法主要依赖于催化剂的光激发，以达到必要的深度还原电位或遭受有限的基板范围。在此，我们证明，cumulenes-有机分子与多个连续的双键-可以作为催化氧化还原介体的电还原自由基硼化（杂）芳基氯在相对温和的阴极电位（约-1.9 V vs.银/氯化银），而不需要光照射。 电化学、光谱学和计算研究支持从还原的累积多烯到电子中性氯代芳烃的逐步电子转移之后是芳基自由基阴离子的化学上有利的介晶裂解以产生所需的芳基自由基中间体。我们的研究结果将指导其他可持续的，纯粹的电还原自由基转化的惰性分子使用有机氧化还原介质的发展。
Single‐electron transfer (SET) plays a critical role in many chemical processes, from organic synthesis to environmental remediation. However, the selective reduction of inert substrates (Ep/2<−2 V vs Fc/Fc+), such as ubiquitous electron‐neutral and electron‐rich (hetero)aryl chlorides, remains a major challenge. Current approaches largely rely on catalyst photoexcitation to reach the necessary deeply reducing potentials or suffer from limited substrate scopes. Herein, we demonstrate that cumulenes–organic molecules with multiple consecutive double bonds–can function as catalytic redox mediators for the electroreductive radical borylation of (hetero)aryl chlorides at relatively mild cathodic potentials (approximately −1.9 V vs. Ag/AgCl) without the need for photoirradiation. Electrochemical, spectroscopic, and computational studies support that step‐wise electron transfer from reduced cumulenes to electron‐neutral chloroarenes is followed by thermodynamically favorable mesolytic cleavage of the aryl radical anion to generate the desired aryl radical intermediate. Our findings will guide the development of other sustainable, purely electroreductive radical transformations of inert molecules using organic redox mediators.