Photoinduced, Copper-Catalyzed Alkylation of Amines: A Mechanistic Study of the Cross-Coupling of Carbazole with Alkyl Bromides.
Photoinduced, Copper-Catalyzed Alkylation of Amines: A Mechanistic Study of the Cross-Coupling of Carbazole with Alkyl Bromides.
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DOI：
10.1021/jacs.7b07052
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发表时间：
2017-09-13
影响因子：
15
通讯作者：
Peters JC
中科院分区：
文献类型：
--
作者：
Ahn JM;Ratani TS;Hannoun KI;Fu GC;Peters JC
我们最近报道，通过使用光和铜催化剂，可以在温和的条件下(−40至30°C)实现氮、硫、氧和碳亲核试剂与有机卤化物的各种偶联。深入了解这些反应进行的各种机理可能会加深我们对化学反应活性的理解，并有助于开发新的方法。在这份报告中，我们应用了一系列的工具(EPR、核磁共振、瞬时吸收和UV-Vis光谱；ESI-MS；X射线结晶学；密度泛函计算；反应性、立体化学和产物研究)来研究咔唑和烷基溴化物的光诱导、铜催化偶联。我们的观察结果与铜(I)咔唑络合物的激发态([CuI(Carb)2]−)和亲核试剂(Li(Carb))的激发态都可以作为烷基溴的光还原剂的路径是一致的。催化的主导途径是Li(Carb)的激发态，生成咔基和烷基。铜通过[CuI(Carb)2]−和[CuII(Carb)3]−(Carb=Carbazolide)是关键中间体，而[CuII(Carb)3]−是主要的交叉偶联的持久自由基，铜通过笼外机制催化这些自由基的交叉偶联。这项研究强调了铜(II)络合物在与自由基中间体结合方面的多功能性，这些中间体是由不同的途径产生的，在通往靶向键结构的途中。
We have recently reported that a variety of couplings of nitrogen, sulfur, oxygen, and carbon nucleophiles with organic halides can be achieved under mild conditions (−40 to 30 °C) through the use of light and a copper catalyst. Insight into the various mechanisms by which these reactions proceed may enhance our understanding of chemical reactivity and facilitate the development of new methods. In this report, we apply an array of tools (EPR, NMR, transient absorption, and UV–vis spectroscopy; ESI–MS; X-ray crystallography; DFT calculations; reactivity, stereochemical, and product studies) to investigate the photoinduced, copper-catalyzed coupling of carbazole with alkyl bromides. Our observations are consistent with pathways wherein both an excited state of the copper(I) carbazolide complex ([CuI(carb)2]− ), and an excited state of the nucleophile (Li(carb)), can serve as photoreductants of the alkyl bromide. The catalytically dominant pathway proceeds from the excited state of Li(carb), generating a carbazyl radical and an alkyl radical. The cross-coupling of these radicals is catalyzed by copper via an out-of-cage mechanism in which [CuI(carb)2]− and [CuII(carb)3]− (carb = carbazolide), both of which have been identified under coupling conditions, are key intermediates, and [CuII(carb)3]− serves as the persistent radical that is responsible for predominant cross-coupling. This study underscores the versatility of copper(II) complexes in engaging with radical intermediates that are generated by disparate pathways, en route to targeted bond constructions.
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影响因子：
15
作者：
Ratani TS;Bachman S;Fu GC;Peters JC
通讯作者：
Peters JC
影响因子：
56.9
作者：
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通讯作者：
Peters, Jonas C.
影响因子：
5.4
作者：
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影响因子：
18.2
作者：
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通讯作者：
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影响因子：
62.1
作者：
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通讯作者：
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