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Upstream product

• 98055-06-2 2-(2-phenylethyl)-1H-indole 
• 736184-66-0 2-(4-phenylbut-1-ynyl)phenylamine 
• 16520-62-0 4-Phenyl-1-butyne 
• 615-43-0 2-iodophenylamine 

Relevant academic research and scientific papers

A Synthetic Route to Chiral Benzo-Fused N-Heterocycles via Sequential Intramolecular Hydroamination and Asymmetric Hydrogenation of Anilino-Alkynes

An efficient sequential intramolecular hydroamination/asymmetric hydrogenation reaction under catalysis of a single chiral ruthenium complex or a binary system consisting of achiral gold complex and chiral ruthenium complex has been reported. A diverse range of enantioenriched benzo-fused N-heterocycles, including 1,2,3,4-tetrahydroquinoline, indoline, and 2,3,4,5-tetrahydro-1H-benzo[b]azepine derivatives, were obtained from anilino-alkynes in high yields (up to 98%) with moderate to excellent enantioselectivities (up to 98% ee) under mild conditions. This protocol features good functional group tolerance and high atom economy. Furthermore, this catalytic protocol is applicable to gram-scale synthesis of a naturally occurring alkaloid, (-)-Angustureine.

Homogenous Pd-catalyzed asymmetric hydrogenation of unprotected indoles: Scope and mechanistic studies

An efficient palladium-catalyzed asymmetric hydrogenation of a variety of unprotected indoles has been developed that gives up to 98% ee using a strong Br?nsted 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 1H 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 Br?nsted 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.

Pd-catalyzed asymmetric hydrogenation of unprotected indoles activated by bronsted acids

The first highly enantioselective hydrogenation of simple indoles was developed with a Brnsted acid as an activator to form the iminium intermediate in situ, which was hydrogenated using Pd(OCOCF3)2/(R)-H8- BINAP catalyst system with up to 96% ee. The present method provides an efficient route to enantioenriched 2-substituted and 2,3-disubstituted indolines.