Conjugate Addition vs Heck Reaction: A Theoretical Study on Competitive Coupling Catalyzed by Isoelectronic Metal (Pd(II) and Rh(I))

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	Conjugate Addition vs Heck Reaction: A Theoretical Study on Competitive Coupling Catalyzed by Isoelectronic Metal (Pd(II) and Rh(I))
	Peng Q(彭谦) ; Yan H(鄢红) ; Zhang XH(张新豪) ; Wu YD(吴云东)
刊名	J. Org. Chem.
	2012
卷号	77 期号:17 页码:7487-7496
ISSN号	0022-3263
其他题名	Pd2+ 和Rh+催化的共轭加成和Heck反应的理论研究
通讯作者	吴云东
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.
学科主题	金属有机化学
收录类别	SCI
原文出处	http://dx.doi.org/10.1021/jo301319j
语种	英语
WOS记录号	WOS:000308390100030
公开日期	2013-08-22
内容类型	期刊论文
源URL	[http://202.127.28.38/handle/331003/28161]
专题	上海有机化学研究所_金属有机化学国家重点实验室
推荐引用方式 GB/T 7714	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.
APA	彭谦,鄢红,张新豪,&吴云东.(2012).Conjugate Addition vs Heck Reaction: A Theoretical Study on Competitive Coupling Catalyzed by Isoelectronic Metal (Pd(II) and Rh(I)).J. Org. Chem.,77(17),7487-7496.
MLA	彭谦,et al."Conjugate Addition vs Heck Reaction: A Theoretical Study on Competitive Coupling Catalyzed by Isoelectronic Metal (Pd(II) and Rh(I))".J. Org. Chem. 77.17(2012):7487-7496.