高等学校化学学报2018，Vol.39Issue(7)：1475-1482,8.DOI:10.7503/cjcu20180117
镍配合物催化N-烯丙基酰胺异构化反应机理
Reaction Mechanism of Nickel Complex Catalyzed Isomerization of N-Allylamides
摘要
Abstract
Reaction mechanism of Ni(PPh3)2-catalyzed isomerization of N-allylamides to generate N-propenylamides was studied theoretically in detail by using density functional theory(DFT)method.The C—H bond activation,isomerization,and reductive elimination to form new C—H bond steps were involved.For C—H bond activation and isomerization steps,Ni(PPh3)2and Ni(PPh3)with only one PPh3ligand were considered and found that the former was more active than the later for these two steps.Both π-allyl and σ-al-lyl mechanisms were calculated for isomerization and found that the π-allyl mechanism was preferred kinetical-ly to the σ-allyl one.The rate-determining energy barrier to generate the E isomer of product is 141.8 kJ/mol,close to that of 141.1 kJ/mol to generate the Z isomer,in agreement with the experimental result that E/Z=56/44.Considering Pd(PPh3)2as the catalyst active species,it is found that the rate-determining energy bar-riers for the formation of E and Z isomers are more than 175 kJ/mol,consistent with the experimental observa-tion that Pd(PPh3)4showed no reactivity.The difference of reactivity between Ni(PPh3)2and Pd(PPh3)2 can be understood from the more strong back-donation of d electrons from Ni to π?anti-bonding orbital of allyl anion comparing with Pd.In addition,the influence of substituents in reactants on E/Z selectivity has been analyzed and found that the steric repulsion between substituents and Ph of PPh3in the rate-determining tran-sition states to generate E and Z isomers induces the difference of E/Z selectivity.关键词
C—H键活化/烯烃异构化/π-烯丙基/σ-烯丙基/N-丙烯基酰胺Key words
C—H Bond activation/Alkene isomerization/π-Allyl/σ-Allyl/N-Propenylamide分类
化学化工引用本文复制引用
方升,王梅艳,刘静静,刘靖尧..镍配合物催化N-烯丙基酰胺异构化反应机理[J].高等学校化学学报,2018,39(7):1475-1482,8.基金项目
国家自然科学基金(批准号:21203073)资助.Supported by the National Natural Science Foundation of China(No.21203073). （批准号:21203073）
