Zhang Jing-Wen, Liu Xiao-Jun, Zhang Jian, Liu Jian-Biao
College of Chemistry, Chemical Engineering and Materials Science, Shandong Normal University, Jinan 250014, China.
Institute of Medical Science, The Second Hospital, Cheeloo College of Medicine, Shandong University, Jinan 250033, China.
Dalton Trans. 2023 Oct 10;52(39):13946-13954. doi: 10.1039/d3dt02570e.
The influence of the P-M-P bite angle in diphosphine ligands on selectivity has been observed in various catalytic reactions. A better understanding of the ligand bite angle concept is important for the rational design of efficient catalytic systems. In the present work, the mechanism of cobalt-catalyzed C-H functionalization of aldehydes with enynes and how the diphosphine ligands alter regioselectivity were investigated by density functional theory (DFT) calculations. The catalytic cycle is initiated by the oxidative cyclization of enynes rather than the oxidative addition of aldehydes. Regioselectivity arises from competing σ-bond metathesis and migratory insertion steps, in which the steric effects of diphosphine ligands are the dominant factors influencing the activation barriers. The calculations indicate that σ-bond metathesis is more challenging and its feasibility is highly dependent on the ligand bite angle. The improved mechanistic understanding will enable further design of transition-metal-catalyzed selective cyclization reactions.
在各种催化反应中，已观察到二膦配体中P-M-P咬角对选择性的影响。更好地理解配体咬角概念对于合理设计高效催化体系至关重要。在本工作中，通过密度泛函理论（DFT）计算研究了钴催化的醛与烯炔的C-H官能化反应机理以及二膦配体如何改变区域选择性。催化循环由烯炔的氧化环化而非醛的氧化加成引发。区域选择性源于竞争的σ键复分解和迁移插入步骤，其中二膦配体的空间效应是影响活化能垒的主要因素。计算表明，σ键复分解更具挑战性，其可行性高度依赖于配体咬角。对机理的深入理解将有助于进一步设计过渡金属催化的选择性环化反应。
