Mechanism and stereoselectivity of benzylic C-H hydroxylation by Ru-porphyrin: a computational study
Mechanism and stereoselectivity of benzylic C-H hydroxylation by Ru-porphyrin: a computational study
复制标题
Ru-卟啉对苄基 C–H 羟基化的机理和立体选择性：计算研究
DOI：
10.1039/c9ob02415h
复制
发表时间：
2020
影响因子：
3.2
通讯作者：
She Yuan-Bin
中科院分区：
文献类型：
--
作者：
Chen Xiahe;Wang Qunmin;Shen Haimin;Li Guijie;Yang Yun-Fang;She Yuan-Bin
通过密度泛函理论计算，阐明了钌卟啉不对称苄基C-H羟基化反应的立体选择性的机理和起源。该反应通过氢原子夺取/氧反弹途径进行，其中高价的-氧代物质从中夺取氢原子以生成自由基对中间体，然后通过氧反弹过程形成1-苯基乙醇。氢原子提取步骤是速率和立体选择性决定步骤。基于该机理模型，计算的立体选择性与实验结果相一致。扭曲/相互作用模型的分析表明，立体选择性是由两个扭曲的能量和之间的相互作用能的手性钌卟啉的扭曲能量。钌卟啉的苯基与大取代基之间的空间排斥作用是导致手性诱导的主要原因。
The mechanism and origin of the stereoselectivity of asymmetric benzylic C–H hydroxylation by Ru–porphyrin were elucidated with density functional theory calculations. The reaction proceeds via a hydrogen-atom abstraction/oxygen-rebound pathway, wherein a high-valent ruthenium-oxo species abstracts a hydrogen atom from ethylbenzene to generate a radical pair intermediate, followed by the oxygen-rebound process to form 1-phenylethanol. The hydrogen-atom abstraction step is the rate- and stereoselectivity-determining step. Based on the mechanistic model, the computed stereoselectivity is in agreement with the experimental observations. Analysis of the distortion/interaction model suggests that stereoselectivity is determined by both the distortion energy of the ethylbenzene and the interaction energy between the ethylbenzene and the chiral Ru–porphyrin. The steric repulsion between the phenyl group of ethylbenzene and the bulky substituent of Ru–porphyrin is the leading cause of chiral induction.