Homogenous Pd-Catalyzed Asymmetric Hydrogenation of Unprotected Indoles: Scope and Mechanistic Studies

	Homogenous Pd-Catalyzed Asymmetric Hydrogenation of Unprotected Indoles: Scope and Mechanistic Studies
	Duan, Ying 1; Li, Lu 2; Chen, Mu-Wang 1; Yu, Chang-Bin 1; Fan, Hong-Jun 1; Zhou, Yong-Gui 1
刊名	journal of the american chemical society
	2014-05-28
卷号	136 期号:21 页码:7688-7700
通讯作者	樊红军 ; 周永贵
英文摘要	an efficient palladium-catalyzed asymmetric hydrogenation of a variety of unprotected indoles has been developed that gives up to 98% ee using a strong bronsted acid as the activator. this methodology was applied in the facile synthesis of biologically active products containing a chiral indoline skeleton. the mechanism of pd-catalyzed asymmetric hydrogenation was investigated as well. isotope-labeling reactions and esi-hrms proved that an iminium salt formed by protonation of the c=c bond of indoles was the significant intermediate in this reaction. the important proposed active catalytic pd-h species was observed with h-1 nmr spectroscopy. it was found that proton exchange between the pd-h active species and solvent trifluoroethanol (tfe) did not occur, although this proton exchange had been previously observed between metal hydrides and alcoholic solvents. density functional theory calculations were also carried out to give further insight into the mechanism of pd-catalyzed asymmetric hydrogenation of indoles. this combination of experimental and theoretical studies suggests that pd-catalyzed hydrogenation goes through a stepwise outer-sphere and ionic hydrogenation mechanism. the activation of hydrogen gas is a heterolytic process assisted by trifluoroacetate of pd complex via a six-membered-ring transition state. the reaction proceeds well in polar solvent tfe owing to its ability to stabilize the ionic intermediates in the pd-h generation step. the strong bronsted acid activator can remarkably decrease the energy barrier for both pd-h generation and hydrogenation. the high enantioselectivity arises from a hydrogen-bonding interaction between n-h of the iminium salt and oxygen of the coordinated trifluoroacetate in the eight-membered-ring transition state for hydride transfer, while the active chiral pd complex is a typical bifunctional catalyst, effecting both the hydrogenation and hydrogen-bonding interaction between the iminium salt and the coordinated trifluoroacetate of pd complex. notably, the pd-catalyzed asymmetric hydrogenation is relatively tolerant to oxygen, acid, and water.
学科主题	物理化学
WOS标题词	science & technology ; physical sciences
类目[WOS]	chemistry, multidisciplinary
研究领域[WOS]	chemistry
关键词[WOS]	highly enantioselective synthesis ; n-heterocyclic carbene ; d-2/d-4 receptor antagonists ; heteroaromatic-compounds ; aerobic oxidation ; molecular-oxygen ; rhodium complex ; ii-hydride ; isoquinolinium salts ; palladium(i) hydride
收录类别	SCI ; IC
语种	英语
WOS记录号	WOS:000336635400035
公开日期	2016-05-09
内容类型	期刊论文
源URL	[http://cas-ir.dicp.ac.cn/handle/321008/144188]
专题	大连化学物理研究所_中国科学院大连化学物理研究所
作者单位	1.Chinese Acad Sci, Dalian Inst Chem Phys, State Key Lab Mol React Dynam, Dalian 116023, Peoples R China 2.Dalian Univ Technol, Sch Chem Engn, Inst Coal Chem Engn, State Key Lab Fine Chem, Dalian 116024, Peoples R China
推荐引用方式 GB/T 7714	Duan, Ying,Li, Lu,Chen, Mu-Wang,et al. Homogenous Pd-Catalyzed Asymmetric Hydrogenation of Unprotected Indoles: Scope and Mechanistic Studies[J]. journal of the american chemical society,2014,136(21):7688-7700.
APA	Duan, Ying,Li, Lu,Chen, Mu-Wang,Yu, Chang-Bin,Fan, Hong-Jun,&Zhou, Yong-Gui.(2014).Homogenous Pd-Catalyzed Asymmetric Hydrogenation of Unprotected Indoles: Scope and Mechanistic Studies.journal of the american chemical society,136(21),7688-7700.
MLA	Duan, Ying,et al."Homogenous Pd-Catalyzed Asymmetric Hydrogenation of Unprotected Indoles: Scope and Mechanistic Studies".journal of the american chemical society 136.21(2014):7688-7700.