Ni(0)催化炔醛偶联反应中配体作用的理论研究  

Ligand effect on nickle-catalyzed reductive alkyne-aldehyde coupling reactions: a computational study

作　　者：罗小玲[1,2] 李英姿[2] 戚孝天[2] 朱磊[2] 陈昌国[2] 蓝宇[2] Xiaoling Luo Yingzi Li Xiaotian Qi Lei Zhtl Changguo Chen Yu Lan(College of Chemistry, Chongqing Normal University, Chongqing 401331, China School of Chemistry and Chemical Engineering, Chongqing University, Chongqing 400030, China)

机构地区：[1]重庆师范大学化学学院,重庆401331 [2]重庆大学化学化工学院,重庆400030

出　　处：《中国科学：化学》2017年第3期341-349,共9页SCIENTIA SINICA Chimica

基　　金：国家自然科学基金(编号:21372266;51302327);中央高校(重庆大学)基础研究经费(编号:106112015CDJZR228806)资助项目

摘　　要：本文运用密度泛函理论(DFT)计算,研究了Ni(0)催化炔烃与醛分子间还原偶联反应的机理,确定了该反应最优反应路径是氧化环化、转金属以及还原消除.计算结果表明,无论使用IMes还是SIPr作为配体,反应的区域选择性都由氧化环化步控制;而硅烷的转金属化是整个反应的决速步.这不同于以往对Ni(0)催化炔醛还原偶联反应的理论研究.理论计算表明,当使用IMes作为配体时,主要产物为2-甲基-3-苯基烯丙基硅醚;当使用SIPr作为配体时,主产物则是3-甲基-2-苯基烯丙基硅醚.无论从主产物还是区域选择性,本文的计算结果都与实验报道一致.本文使用反应路径形变-结合能模型研究了IMes作为配体时的区域选择性.结果表明,形成主产物时具有较低的形变能.也就是说,过渡态中炔烃部分与苯基折叠程度较小,共轭程度更大,因此主产物为2-甲基-3-苯基烯丙基硅醚.本课题组还使用2D投影图模型研究了空间效应对不同配体的影响.结果表明,当使用IMes配体时,由于配体体积较小,可以容纳苯基在其周围,从而减小了炔烃上的苯基与醛上苯基的排斥;而使用大位阻的SIPr作为配体时,配体与炔烃上的苯基排斥很大,从而不利于2-甲基-3-苯基烯丙基硅醚的生成.Density functional theory（DFT） calculations were employed to study Ni（0）-catalyzed reductive coupling of alkyne and aldehyde. The mechanism of that reaction is determined to consist of oxidative cyclization, transmetalation and reductive elimination. Theoretical calculations indicate that, no matter IMes or SIPr were used as ligand, the regioselectivity would be controlled by the oxidative cyclization step and the rate-limiting step is the transmetalation of silane, which is different from previous theoretical and experimental studies. In our computational results, 2-methyl-3-phenyl-allyl silyl ether 5 is confirmed to be the main product when IMes is used as ligand, whereas allyl-3-methyl-2-phenyl-silyl ether 4 is calculated to be main product using SIPr as ligand. Distortion-interaction energy analysis along the whole reaction pathways indicate that when IMes is used as the ligand, the oxidative cyclization transition state 8-ts has lower distortion energy due to the smaller distortional angle of alkyne substituents. Moreover, 2D contour maps analysis was used to investigate the difference of regioselectivity with IMes and SIPr ligands. The computational results suggest that the smaller bulkiness of IMes can tolerate phenyl around it, thus decreasing the repulsion of phenyl in alkyne with that in aldehyde. On the other hand, when the more bulky ligand SIPr was used, the formation of 2-methyl-3-phenyl-allyl silyl ether 5 would be unfavored due to the large steric repulsion.

关 键 词：烃与醛还原偶联 DFT计算 形变-结合能模型 空间位阻效应 Ni催化 

分 类 号：O621.251[理学—有机化学]