锰催化苄基C—H键氟化反应机理的理论研究  

Theoretical study on the mechanism for benzylic C—H fluorination catalyzed by manganese complex

作　　者：霍瑞萍 张祥 张彩凤[1,3] HUO Rui-ping;ZHANG Xiang;ZHANG Cai-feng(Taiyuan Normal University,Department of Chemistry,Jinzhong 030619,China;School of Chemistry and Materials Science,Shanxi Normal University,Linfen 041004,China;Humic Acid Engineering and Technology Research Center of Shanxi,Jinzhong 030619,China)

机构地区：[1]太原师范学院,山西晋中030619 [2]山西师范大学,山西临汾041004 [3]山西省腐植酸工程技术研究中心,山西晋中030619

出　　处：《化学研究与应用》2021年第3期444-453,共10页Chemical Research and Application

基　　金：山西省应用基础研究项目(201801D221080,201801D121257);山西省高等科技创新项目(2019L0814)资助;国家自然科学基金青年基金项目(21804098)资助;太原师范学院青年学术带头人项目资助;太原师范学院博士启动经费项目资助;山西省“1331计划”协同创新中心项目资助。

摘　　要：采用密度泛函理论(Density Functional Theory,DFT),对锰催化剂Mn^(III)(salene)F作用下苄基C—H键氟化反应的机理进行了深入的理论研究。对该反应中涉及到的重要中间体和过渡态的能量、Mulliken电荷分布、前线分子轨道等进行了分析。计算结果表明采用[Mn^(IV)(OH)(salene)F]和[Mn^(IV)(salene)F_(2)]为催化剂催化苄基C—H键氟化反应所需的能垒分别为11.5 kcal·mol^(-1)和7.6 kcal·mol^(-1)。可见采用双氟催化剂[Mn^(IV)(salene)F_(2)],氟化反应的能垒较低,更有利于苄基C—H键的氟化。通过轨道分析,给出了反应过程中详细的电子转移情况,从本质上分析了苄基氟化反应的机理。研究表明中心金属上的氧原子可以获得和失去电子,在C—H活化过程中起到传递电子的作用。在电子转移过程中,Mn原子是最终的电子接受体。以上结果很好地解释了实验现象,为进一步研究金属催化C—H键氟化反应提供理论支持。The mechanism of manganese complex(MnIII(salene)F)catalyzed benzylic C—H fluorination has been investigated using density functional theory(DFT).The energies,Mulliken charge populations and frontier molecular orbital characteristics of key intermediates and transition states involved in the reaction were analyzed.The results showed that the rate determining energy barriers for the fluorination of benzyl C—H bond catalyzed by[Mn^(IV)(OH)(salene)F]and[Mn^(IV)(salene)F_(2)]are 11.5 kcal·mol^(-1) and 7.6 kcal·mol^(-1),respectively.These results suggested that difluorinated catalyst[Mn^(IV)(salene)F_(2)]has advantage in lowering the reaction temperature superior to monofluorinated catalyst[Mn^(IV)(OH)(salene)F].Detailed electron transfer in the reaction process is given by orbital analysis.The mechanism of benzyl C—H bond fluorination reaction is analyzed in essence.The Oxygen atom was demonstrated to be the electron transport media,acting as both the electron acceptor and donor in the process of C—H activation.Mn atom acts as the final electron acceptor in the electron transport.The calculated results preferably explain the experimental phenomena and provide a theory support for metal catalyzed C—H fluorination.The calculated results preferably explain the experimental phenomena and provide a theoretical support for metal catalyzed benzyl fluorination.

关 键 词：锰催化 苄基C—H键氟化反应 密度泛函计算 机理 

分 类 号：O641[理学—物理化学]