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学科主题: 金属有机化学
题名: Conjugate Addition vs Heck Reaction: A Theoretical Study on Competitive Coupling Catalyzed by Isoelectronic Metal (Pd(II) and Rh(I))
其他题名: Pd2+ 和Rh+催化的共轭加成和Heck反应的理论研究
作者: Peng Q(彭谦) ; Yan H(鄢红) ; Zhang XH(张新豪) ; Wu YD(吴云东)
通讯作者: 吴云东
刊名: J. Org. Chem.
发表日期: 2012-01-01
卷: 77, 期:17, 页:7487-7496
收录类别: SCI
部门归属: 中科院上海有机化学研究所; 香港科技大学
英文摘要: Density functional theory studies have been carried out to investigate the mechanism of the Pd(II(bpy)-and Rh(I)(bpy)-catalyzed conjugate additions and their competitive Heck reactions involving alpha,beta-unsaturated carbonyl compounds. The critical steps of the mechanism are insertion and termination. The insertion step favors 1,2-addition of the vinyl-coordinated species to generate a stable C-bound enolate intermediate, which then may isomerize to either an oxa-pi-allyl species or an O-bound enolate. The termination step involves a competition between beta-hydride elimination, leading to a Heck reaction product, and protonolysis reaction that gives a conjugate addition product. These two pathways are competitive in the Pd(II)-catalyzed reaction, while a preference for protonolysis has been found in the Rh(I)-catalyzed reaction. The calculations are in good agreement with the experimental observations. The potential energy surface and the rate-determining step of the beta-hydride elimination are similar for bcth Pd(II)- and Rh(I)-catalyzed processes. The rate-determining steps of the Pd(II)- and Rh(I)-catalyzed protonolysis are different. Introduction of an N- or P-ligand significantly stabilizes the protonolysis transition state via the O-bound enolate or oxa-pi-allyl complex intermediate, resulting in a reduced free energy of activation. However, the barrier of the beta-hydride elimination is less sensitive to ligands. For the Rh(I)-catalyzed reaction, protonolysis is calculated to be more favorable than the beta-hydride elimination for all investigated N and P ligands due to the significant ligand stabilization to the protonolysis transition state. For the Pd(II)-catalyzed reaction, the complex with monodentate pyridine ligands prefers the Heck-type product through beta-hydride elimination, while the complex with bidentate N and P ligands favors the protonolysis. The theoretical finding suggests the possibility to control the selectivity between the conjugate addition and the Heck reaction by using proper ligands.
语种: 英语
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WOS记录号: WOS:000308390100030
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内容类型: 期刊论文
URI标识: http://ir.sioc.ac.cn/handle/331003/28161
Appears in Collections:金属有机化学国家重点实验室_期刊论文

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Recommended Citation:
Peng Q,Yan H,Zhang XH,et al. Conjugate Addition vs Heck Reaction: A Theoretical Study on Competitive Coupling Catalyzed by Isoelectronic Metal (Pd(II) and Rh(I))[J]. J. Org. Chem.,2012,77(17):7487-7496.
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