Cu-Catalyzed aromatic C-H imidation with N-fluorobenzenesulfonimide: mechanistic details and predictive models.
Cu-Catalyzed aromatic C-H imidation with N-fluorobenzenesulfonimide: mechanistic details and predictive models.
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DOI：
10.1039/c6sc04145k
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发表时间：
2017-02-01
期刊：
影响因子：
8.4
通讯作者：
Musaev DG
中科院分区：
文献类型：
--
作者：
Haines BE;Kawakami T;Kuwata K;Murakami K;Itami K;Musaev DG
双核CuII-CuII中间体是一种NFSI分步双电子氧化反应的活性催化剂，是一种区域选择性预测工具，也是一种新的催化剂开发。我们以前报道过的LCuBr催化的N-氟苯磺酰亚胺（NFSI）对芳烃的C-H酰亚胺化反应，使用廉价的催化剂，适用于广泛的复杂芳烃。计算和实验研究表明，反应机理包括两个部分：（1）活性双核CuII-CuII催化剂的生成;（2）芳烃C-H键亚胺化的催化循环。计算表明，实验中使用的LCuIBr络合物不是活性催化剂。相反，在与NFSI反应时，它转化为使用HRMS技术检测的活性双核CuII-CuII催化剂。从CuII-CuII双核络合物开始的催化循环通过以下步骤进行：（a）通过NFSI对活性催化剂进行单电子氧化，以产生酰亚胺基自由基和双核CuII-CuIII中间体，（B）从芳烃到酰亚胺基自由基的转换限制单电子转移（SET 1），（c）与酰亚胺基阴离子和芳基自由基阳离子的快速C-N键形成，（d）通过芳基还原CuII-CuIII双核中间体以再生活性催化剂并产生芳基阳离子中间体，和（e）芳烃环的去质子化和重排以形成酰亚胺化产物。计算出的KIE的周转限制SET 1步骤再现其实验观察值。开发了一种简单的预测工具，并通过实验验证，以确定给定底物的区域化学结果。我们表明，预反应LCuX配合物，其中X = Cl，Br和I，显示出类似的反应模式，这些配合物转化为相同的催化活性双核CuII-CuII物种。
Dinuclear CuII–CuII intermediate is an active catalyst for an unusual stepwise two-electron oxidation by NFSI, a regioselectivity predictive tool and a new catalyst development. The LCuBr-catalyzed C–H imidation of arenes by N-fluorobenzenesulfonimide (NFSI), previously reported by us, utilizes an inexpensive catalyst and is applicable to a broad scope of complex arenes. The computational and experimental study reported here shows that the mechanism of the reaction is comprised of two parts: (1) generation of the active dinuclear CuII–CuII catalyst; and (2) the catalytic cycle for the C–H bond imidation of arenes. Computations show that the LCuIBr complex used in experiments is not an active catalyst. Instead, upon reacting with NFSI it converts to an active dinuclear CuII–CuII catalyst that is detected using HRMS techniques. The catalytic cycle starting from the CuII–CuII dinuclear complex proceeds via (a) one-electron oxidation of the active catalyst by NFSI to generate an imidyl radical and dinuclear CuII–CuIII intermediate, (b) turnover-limiting single-electron-transfer (SET1) from the arene to the imidyl radical, (c) fast C–N bond formation with an imidyl anion and an aryl radical cation, (d) reduction of the CuII–CuIII dinuclear intermediate by the aryl radical to regenerate the active catalyst and produce an aryl-cation intermediate, and (e) deprotonation and rearomatization of the arene ring to form the imidated product. The calculated KIE for the turnover-limiting SET1 step reproduces its experimentally observed value. A simple predictive tool was developed and experimentally validated to determine the regiochemical outcome for a given substrate. We demonstrated that the pre-reaction LCuX complexes, where X = Cl, Br and I, show a similar reactivity pattern as these complexes convert to the same catalytically active dinuclear CuII–CuII species.