阴离子协助镍催化碳氟键官能团化反应机理研究  

Mechanism investigation for anoin-assisted nickel catalyzed C–F bond functionalization reaction: a DFT study

作　　者：曾珍 张涛[2] 岳小雨 张华 白若鹏 蓝宇[2] Zhen Zeng;Tao Zhang;Xiaoyu Yue;Hua Zhang;Ruopeng Bai;Yu Lan(College of Chemistry ＆ Materials Science,South-Central University for Nationalities,Wuhan 430070,Chin;School of Chemistry and Chemical Engineering,Chongqing University,Chongqing 400030,China;College of Chemistry,Nanchang University,Nanehang 330031,China)

机构地区：[1]中南民族大学化学与材料科学学院,武汉430070 [2]重庆大学化学化工学院,重庆400030 [3]南昌大学化学学院,南昌330031

出　　处：《中国科学：化学》2018年第7期736-742,共7页SCIENTIA SINICA Chimica

基　　金：国家自然科学基金(编号:21772020;21602096);中央高校基本科研业务费(编号:106112017CDJXY220007)资助项目

摘　　要：由于碳-氟键的化学惰性,其高效催化转化一直是有机化学中的难题之一.本文运用密度泛函理论(DFT)计算,研究了镍催化碳-氟/碳-氢键交叉偶联反应构建2-芳基噁唑衍生物的机理.计算结果表明,体系中氟负离子能够稳定零价镍金属催化剂,得到氟负离子配位的阴离子镍活性催化物种.在氟负离子协助下碳-氟键对阴离子镍氧化加成得到二价芳基镍物种,是催化循环的速控步骤.在碳氢键切断过程中,Br?nsted碱直接进攻去质子,得到二芳基镍中间体,最终通过还原消除得到交叉偶联产物.在这一过程中,阴离子镍活性催化物种的稳定性明显高于通常推测的中性镍催化物种,这一模型为理解惰性碳-氟键活化反应机理提供了新的思路.C-F bond functionalization still faces with great challenges in synthetic chemistry due to the inert nature of C-F bond in organic compounds. Herein, the newly reported DFT method M11-L was used to determine the mechanism of nickel catalyzed C-F/C-H bond cross coupling involving the C-F bond cleavage of flouroarenes and C-H bond functionalization of oxazoles. DFT calculations revealed that fluoride would stabilize the nickel（0） compound to afford an active nickel（0） ate-complex. With the assistance of fluoride, the oxidative addition of C-F bond to nickel（0） ate- complex would yield an active nickel（II） species, which is the rate-determining step in this catalytic cycle. The following C-H bond cleavage step would proceed via a direct deprotonation step under the attack of Bronsted base, to generate diarylnickel（II） species. Finally, reductive elimination step would occur to give the coupling product with regeneration of active nickel（0） ate-complex. In this pathway, we found that the relative free energies of nickel ate-complex species are more stable than commonly assumed neutral-nickel intermediates. This work could provide a new way for the mechanism study of inert C-F bond activation reactions.

关 键 词：碳-氟键 密度泛函理论 氟负离子协助 阴离子镍 

分 类 号：O621.251[理学—有机化学]