铑催化去对称氢酰化机制理论研究  

Mechanism of rhodium catalyzed desymmetrization by hydroacylation: a DFT study

作　　者：罗小玲 彭菊 刘松 钟康宝 张涛[2] 陈容 蓝宇[2] Xiaoling Luo;Ju Peng;Song Liu;Kangbao Zhong;Tao Zhang;Rong Chen;Yu Lan(Chongqing Key Laboratory of Inorganic Functional Materials, College of Chemistry, Chongqing Normal University, Chongqing 401331, China;Chongqing Key Laboratory of Theoretical and Computational Chemistry, 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,无机功能材料重庆市重点实验室,重庆401331 [2]重庆大学化学化工学院,理论计算化学重庆市重点实验室,重庆400030

出　　处：《中国科学：化学》2019年第8期1094-1103,共10页SCIENTIA SINICA Chimica

基　　金：国家自然科学基金(编号:21822303,21772020);重庆师范大学博士启动基金(编号:16XLB009)资助项目

摘　　要：本文运用密度泛函理论(DFT)计算,研究了手性双膦络合Rh(I)催化去对称性烯烃氢酰基化反应机理.计算确定了该反应最优反应路径包括醛基C–H键活化、第一个烯基插入Rh–H键、β-H消除、第二个烯基插入Rh–H键以及还原消除.计算结果表明,第一个烯基插入Rh–H键是立体选择性决定步,还原消除反应是整个反应的决速步.我们还通过理论计算研究了可能的烯烃碳酰基化副反应机理.计算预测反应主产物是S构型--季碳环戊酮,与实验报道一致.我们通过非共价弱相互作用分析研究配体对反应化学选择性的影响,结果表明,当使用位阻大的双膦配体(R)-DTBM-MeOBIPHEP时,由于配体与底物的排斥较大,不利于碳酰化反应发生,反应优势产物是烯烃氢酰化产物;而当用空间位阻小的双膦配体BzDPPB时,碳酰化反应变得更加有利,反应主产物为碳酰化产物双环[2.2.1]庚酮.因此,配体的空间位阻决定了Rh(I)催化烯烃酰基化反应的化学选择性.Density functional theory(DFT) calculations were employed to investigate the mechanism and the chemoselectivity of Rh(I)-catalyzed desymmetrization of prochiral by hydroacylation. Detailed calculations show that the hydroacylation reaction occurs through C–H bond activation, allyl migratory insertion,β-H elimination, another allyl migratory insertion into Rh–H bond and reductive elimination. Theoretical calculations indicated that the rate-limiting step of the hydroacylation reaction is the final reductive elimination, while the enantioselectivity of this reaction is determined by the first allyl migratory insertion step. The mechanism of the carboacylation, which is the side reaction for the hydroacylation reaction, was also calculated. The theoretical investigations indicated that the hydroacylation is more favorable than carboacylation, which is agreement with the experimental results. The NCI analysis was introduced to study the chemoselectivity of this hydroacylation reaction. The calculated results suggested that the large steric repulsion between(R)-DTBM-MeOBIPHEP ligand and substrate make the carboacylation difficult to occur, while the carboacylation becomes favorable with BzDPPB as ligand. It can be concluded that the chemoselectivity of this desymmetrization and hydroacylation reaction is controlled by the steric repulsion between the ligand and the substrate.

关 键 词：氢酰化反应 去对称性 DFT计算 碳酰化反应 空间位阻 

分 类 号：O621.251[理学—有机化学]