Zhang Cong, Li Guorong, Shang Zhenfeng, Li Ruifang, Xu Xiufang
Department of Chemistry, Key Laboratory of Advanced Energy Materials Chemistry (Ministry of Education), College of Chemistry, Nankai University, Tianjin 300071, P. R. China.
J Org Chem. 2024 Feb 2;89(3):1505-1514. doi: 10.1021/acs.joc.3c02110. Epub 2024 Jan 13.
The mechanism of the Ni-Al bimetallic-catalyzed C-H cyclization to construct tricyclic imidazoles is investigated using density functional theory calculations. The calculation result shows that the reaction mechanism involves sequential steps of substrate coordination, ligand-to-ligand hydrogen transfer (LLHT), and C-C reductive elimination to produce the final product tricyclic imidazole. The LLHT step is calculated to be the rate-determining step. The oxidative addition of the benzimidazole C-H bond to the Ni center and the insertion of the alkene into the Ni-H bond occur concertedly in the LLHT step. The effects of N-heterocyclic carbene (NHC) ligands and AlMe on the reactivity and regioselectivity were also analyzed. These calculation results shed light on some ambiguous suggestions from experiments.
采用密度泛函理论计算方法研究了镍-铝双金属催化的C-H环化反应构建三环咪唑的机理。计算结果表明，反应机理包括底物配位、配体间氢转移（LLHT）以及C-C还原消除等连续步骤，最终生成三环咪唑产物。计算得出LLHT步骤是速率决定步骤。在LLHT步骤中，苯并咪唑C-H键向镍中心的氧化加成以及烯烃插入镍-氢键的过程协同发生。还分析了氮杂环卡宾（NHC）配体和AlMe对反应活性和区域选择性的影响。这些计算结果为实验中一些模糊的结论提供了依据。
