连续流条件下蒽-铈协同催化的苄位碳氢键选择性氧化反应  

Selectively Aerobic Oxidation of Benzylic C—H Bonds Enabled by Dual Anthracene and Cerium Catalysis under Continuous-Flow Conditions

作　　者：徐袁利 潘辉 杨义 左智伟 Xu Yuanli;Pan Hui;Yang Yi;Zuo Zhiwei(Innovation Center for Chenguang High Performance Fluorine Material,School of Chemical&Environmental Engineering,Sichuan University of Science and Engineering,Zigong,Sichuan 643000;State Key Laboratory of Organometallic Chemistry,Shanghai Institute of Organic Chemistry,Chinese Academy of Sciences,Shanghai 200032)

机构地区：[1]四川轻化工大学化学与环境工程学院晨光高性能氟材料创新中心,四川自贡643000 [2]中国科学院上海有机化学研究所金属有机化学国家重点实验室,上海200032

出　　处：《化学学报》2023年第5期435-440,共6页Acta Chimica Sinica

基　　金：国家自然科学基金(Nos.22125111,21971163);国家重点研发计划(No.2021YFA1500100);基础研究特区计划-中国科学院上海分院、四川省科技计划项目(No.2023NSFSC0097);晨光高性能氟材料创新中心项目(No.SCFZ2201)资助。

摘　　要：苄位氧化反应是有机合成中重要的官能团转化方法之一,但传统的苄位氧化反应通常需要高温和强氧化剂等严苛条件.报道了一种在连续流微反应器中实现的蒽-铈协同催化的苄位选择性氧化反应,使用9,10-二溴蒽(DBA)和铈-醇配合物作为光催化剂,氧气为绿色氧化剂,以很高的效率在室温条件下制备了各种芳香酮类化合物.该体系可以在数分钟内实现完全转化,具有操作简便、反应条件温和、选择性高、废物少和适用性广等优点,并且容易实现规模放大和连续生产.The benzyl oxidation reaction serves as a crucial functional group transformation method in the field of organic synthesis.Regrettably,traditional benzyl oxidation reactions frequently necessitate harsh conditions,such as elevated temperatures and potent oxidizing agents.In contrast,this article showcases a highly selective catalytic benzylic oxidation executed within a continuous-flow microreactor.By harnessing the previously established cerium-alcohol complex’s ligand to metal charge transfer(LMCT)-hydrogen atom transfer(HAT)activation mechanism and the anthracene-cerium synergistic catalytic system,a diverse array of aromatic ketones was synthesized from aryl alkanes with remarkable efficiency under ambient and aerobic conditions.The continuous-flow technology,endowed with unique advantages such as heightened illumination efficiency,superior gas-liquid mass transfer,repeatability,and scalability,has emerged as a powerful instrument for scaling-up photocatalytic reactions.In this process,under flow conditions,ethyl acetate solutions comprising Ce(NO3)3•6H2O,tetrabutylammonium bromide(TBABr),9,10-dibromoanthracene(DBA),trichloroethanol(TCE),and ethylbenzene encountered and mixed with oxygen within the microreactor.Subsequently,a photocatalytic aerobic oxidation reaction occurred under visible light irradiation at room temperature,achieving complete conversion within a mere 5 min,and rapidly generated a series of aromatic ketones with good to excellent yields.Mechanistic studies indicated the paramount importance of the anthracene-derived catalyst DBA in achieving the heightened efficiency.Under visible light irradiation,the excited state DBA was initially oxidatively quenched with oxygen or peroxide species generated in the system,resulting in the formation of the DBA cationic free radical.Subsequently,the DBA cationic free radical underwent a single electron transfer(SET)process with the low-valent cerium(III)complex,consequently expediting the oxidative regeneration of the cerium(IV)catalyst and markedly b

关 键 词：苄位氧化 蒽-铈协同催化 可见光催化 连续流光反应 

分 类 号：O621.251[理学—有机化学]