Mechanistic study of the ligand controlled regioselectivity in iridium catalyzed C-H borylation of aromatic imines.
Mechanistic study of the ligand controlled regioselectivity in iridium catalyzed C-H borylation of aromatic imines.
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铱催化芳族亚胺C-H硼化反应中配体控制的区域选择性机理研究
DOI：
10.1039/c8ra07886f
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发表时间：
2018-10-15
期刊：
影响因子：
3.9
通讯作者：
Yao, Lingmin
中科院分区：
文献类型：
--
作者：
Liu, Yuhua;Chen, Jipei;Zhan, Kangsheng;Shen, Yiqiang;Gao, Hui;Yao, Lingmin
作为C-H硼化反应的一个主要挑战，如何控制反应的选择性引起了人们的广泛关注，然而，相关的机理信息仍有待于揭示。本文采用密度泛函理论（DFT）研究了铱催化的芳香亚胺C-H硼化反应中配体控制的区域选择性的机理。比什特，B。Chattopadhyay，J. Am.化学会，2016，138，84-87）。所提出的Ir（i）-Ir（iii）催化循环包括（i）C-H键与铱（i）的氧化加成;（ii）C-B键的还原消除;（iii）B2 pin 2与铱（i）氢化物络合物的氧化加成;和（iv）B-H键的还原消除。C-H键与铱中心的氧化加成是决定步骤。对于配体AQ，邻位选择性被认为是由于AQ（8-氨基喹啉）的空间位阻降低和给电子效应增加，从而促进了C-H活化的邻位过渡态的质子转移。而对于TMP配体，TMP（4，5，7，8-四甲基-1，10-菲咯啉）与邻位取代亚胺之间的空间排斥阻碍了邻位C-H的活化，有利于Meta硼化反应。我们的计算提供了进一步的配体设计的见解，以实现不同的区域选择性硼化芳烃。在此基础上，通过对配体的电子和空间取代基进行相应的修饰，可以实现芳烃硼化反应的区域选择性。DFT计算表明，在铱催化的芳烃C-H硼化反应中，邻位选择性是由于AQ配体的给电子效应，Meta选择性是由于TMP配体的空间位阻效应。
As a major challenge in C–H borylation, how to control the selectivity has attracted lots of attention, however, the related mechanistic information still needs to be uncovered. Herein, density functional theory (DFT) has been used to study the mechanism for the ligand controlled regioselectivity in the iridium-catalyzed C–H borylation of aromatic imines, which is inspired by experimental observations (R. Bisht, B. Chattopadhyay, J. Am. Chem. Soc., 2016, 138, 84–87). The proposed Ir(i)–Ir(iii) catalytic cycle includes (i) the oxidative addition of the C–H bond to iridium(i); (ii) the reductive elimination of a C–B bond; (iii) the oxidative addition of B2pin2 to an iridium(i) hydride complex; and (iv) the reductive elimination of a B–H bond. The oxidative addition of a C–H bond to the iridium center is the determining step. For the ligand AQ, ortho-selectivity is proposed to be attributed to the decreased steric hindrance and increased electron donating effect of AQ (8-aminoquinoline) which promotes proton-transfer in the ortho-transition state of C–H activation. While, for the TMP ligand, the steric repulsion between the TMP (4,5,7,8-tetramethyl-1, 10-phenanthroline) ligand and the ortho-substituted imine hinders the ortho C–H activation and favors meta borylation. Our calculations provide insights into further ligand design to achieve different regioselective borylation of aromatics. Guided by the results, the regioselectivity in the borylation of aromatics may be achieved by accordingly modifying the electronic and steric substituents of the ligand. DFT calculation indicates that in iridium catalyzed C–H borylation of aromatics, the ortho selectivity is proposed to be attributed to the electron donating effect of AQ ligand, while the meta selectivity is due to steric hindrance of TMP ligand.
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影响因子：
15
作者：
Maleczka, RE;Shi, F;Smith, MR
通讯作者：
Smith, MR
影响因子：
4.4
作者：
DOLG, M;WEDIG, U;PREUSS, H
通讯作者：
PREUSS, H
影响因子：
15
作者：
Chattopadhyay B;Dannatt JE;Andujar-De Sanctis IL;Gore KA;Maleczka RE Jr;Singleton DA;Smith MR 3rd
通讯作者：
Smith MR 3rd
影响因子：
15
作者：
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通讯作者：
Hartwig, John F.
影响因子：
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作者：
BECKE, AD
通讯作者：
BECKE, AD