90874-56-9Relevant academic research and scientific papers
Pd/C-Catalyzed transfer hydrogenation ofN-H indoles with trifluoroethanol and tetrahydroxydiboron as the hydrogen source
Zhou, Xiao-Yu,Chen, Xia
supporting information, p. 548 - 551 (2021/02/06)
Under the guidance of the known mechanism of the hydrogenation of indoles and transfer hydrogenation with tetrahydroxydiboron (B2(OH)4), Pd/C catalyzed transfer hydrogenation ofN-H indoles with trifluoroethanol and tetrahydroxydiborane as the hydrogen source has been developed. This provides an efficient strategy and catalytic system for the reduction of un-activatedN-H indoles, andN-H indolines are obtained with good to excellent yields. In addition, a series of the isotopic labelling experiments were carried out to probe the mechanism.
Kinetic Resolution of 2-Substituted Indolines by N-Sulfonylation using an Atropisomeric 4-DMAP-N-oxide Organocatalyst
Murray, James I.,Flodén, Nils J.,Bauer, Adriano,Fessner, Nico D.,Dunklemann, Daniel L.,Bob-Egbe, Opetoritse,Rzepa, Henry S.,Bürgi, Thomas,Richardson, Jeffery,Spivey, Alan C.
supporting information, p. 5760 - 5764 (2017/05/12)
The first catalytic kinetic resolution by N-sulfonylation is described. 2-Substituted indolines are resolved (s=2.6–19) using an atropisomeric 4-dimethylaminopyridine-N-oxide (4-DMAP-N-oxide) organocatalyst. Use of 2-isopropyl-4-nitrophenylsulfonyl chloride is critical to the stereodiscrimination and enables facile deprotection of the sulfonamide products with thioglycolic acid. A qualitative model that accounts for the stereodiscrimination is proposed.
METHOD FOR PRODUCING OPTICALLY ACTIVE COMPOUND, AND NOVEL METAL-DIAMINE COMPLEX
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Paragraph 0298; 0299, (2016/12/22)
The present invention pertains to a method for producing an optically active compound which includes a step for reducing an imino group of an imine compound or a step for reducing an unsaturated bond of a heterocyclic compound, while in the presence of hydrogen gas as a hydrogen donor and one or more types of complexes selected from a group consisting of a complex represented by general formula (1), a complex represented by general formula (2), a complex represented by general formula (3), and a complex represented by general formula (4) (the general formulas (1)-(4) are as stipulated by claim 1).
Homogenous Pd-catalyzed asymmetric hydrogenation of unprotected indoles: Scope and mechanistic studies
Duan, Ying,Li, Lu,Chen, Mu-Wang,Yu, Chang-Bin,Fan, Hong-Jun,Zhou, Yong-Gui
supporting information, p. 7688 - 7700 (2014/06/10)
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.
Novel strategies for the solid phase synthesis of substituted indolines and indoles
Nicolaou,Roecker,Hughes, Robert,Van Summeren, Ruben,Pfefferkorn, Jeffrey A.,Winssinger, Nicolas
, p. 465 - 476 (2007/10/03)
Using a polymer-bound selenenyl bromide resin, o-allyl and o-prenyl anilines were cycloaded to afford a series of solid-supported indoline and indole scaffolds. These scaffolds were then functionalized and cleaved via four distinct methods, namely traceless reduction, radical cyclization, radical rearrangement, and oxidative elimination, to afford 2-methyl indolines, polycyclic indolines, 2-methyl indoles, and 2-propenyl indolines, respectively. A number of small combinatorial libraries of compounds reminiscent of certain designed ligands of biological interest were constructed demonstrating the potential utility of the developed methodology to chemical biology studies and the drug discovery process.
