A theoretical study of dirhodium-catalyzed intramolecular aliphatic C-H bond amination of aryl azides
A theoretical study of dirhodium-catalyzed intramolecular aliphatic C-H bond amination of aryl azides
复制标题
二铑催化芳基叠氮化物分子内脂肪族C-H键胺化的理论研究
DOI：
10.1039/c5ra24340h
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发表时间：
2016
期刊：
影响因子：
3.9
通讯作者：
Zhao Cunyuan
中科院分区：
文献类型：
--
作者：
Xu Huiying;Zhang Xuepeng;Ke Zhuofeng;Zhao Cunyuan
用BPW 91功能化反应器研究了含铑催化剂介导的芳基叠氮化合物的脂肪族C-H键胺化反应。计算表明，以Rh 2（esp）2（esp = α，α，α′，α′-四甲基-1，3-苯二丙酸）和模型化合物Rh 2（OCHO）4为催化剂时，反应机理相似.首先，铑金属配合物与衬底配位并释放氮气。该速率决定步骤导致金属氮烯的形成。金属氮烯介导的分子内C-H键胺化反应分别通过两种途径进行。单重态金属氮烯介导的分子内C-H键胺化反应是通过一个协同和异步的途径发生的，该途径涉及金属氮烯直接插入C-H键。三重态金属氮宾的情况是一个逐步的途径，涉及氢转移，然后双自由基重组。我们的研究表明，三重态H-提取比单重态H-提取更有利。所得的三重态中间体不会经过高势垒双自由基重组过程，而是通过MECP穿过单线态途径并形成最终的单线态产物。Rh 2（esp）2中的esp配体提供了空间位阻效应来限制底物-催化剂化合物，但对铑催化芳基叠氮化合物的脂肪族C-H键胺化反应机理影响不明显。
Dirhodium-contained catalysts mediated aliphatic C–H bond amination of aryl azides were studied using BPW91 functional. Calculations show the reactions with Rh2(esp)2 (esp = α,α,α′,α′-tetramethyl-1,3-benzenedipropionic acid) and the model compound Rh2(OCHO)4 as catalysts take place via similar mechanisms. Firstly, the dirhodium metal complex coordinates with the substrate and releases nitrogen gas. This rate-determining step results in the formation of the metal nitrene. Metal nitrene mediated intramolecular C–H bond amination is conducted via two alternative pathways, respectively. The singlet metal nitrene mediated intramolecular C–H bond amination occurs via a concerted and asynchronous pathway involving direct metal nitrene insertion into the C–H bond. The triplet metal nitrene case is a stepwise pathway involving a hydrogen transfer and then a diradical recombination. Our study suggests the triplet H-abstraction is more favorable than the singlet one. The resulted triplet intermediate would not go through the high-barrier diradical recombination process, but across to the singlet pathway via a MECP and form the final singlet product. The tethered esp ligands in Rh2(esp)2 provide steric effects to constrain the substrate-catalyst compound but indicates inconspicuous influence on the mechanisms of dirhodium catalyzed aliphatic C–H bond amination of aryl azides.