1775-86-6Relevant articles and documents
Diboron-mediated palladium-catalyzed asymmetric transfer hydrogenation using the proton of alcohols as hydrogen source
Wu, Bo,Yang, Jimin,Hu, Shu-Bo,Yu, Chang-Bin,Zhao, Zi-Biao,Luo, Yi,Zhou, Yong-Gui
, p. 1743 - 1749 (2021/09/06)
The developments of hydrogen sources stand at the forefront of asymmetric reduction. In contrast to the well-studied alcohols as hydrogen sources via β-hydride elimination, the direct utilization of the proton of alcohols as a hydrogen source for activator-mediated asymmetric reduction is rarely explored. Herein we report the proton of alcohols as a hydrogen source in diboron-mediated palladium-catalyzed asymmetric transfer hydrogenation of 1,3-diketones and indoles, providing a series of chiral β-hydroxy ketones and indolines with excellent yields and enantioselectivities. This strategy would be useful for the synthesis of chiral deuterium-labelled compounds due to the ready availability of deuterium-labelled alcohols. Mechanistic investigations and DFT calculations revealed that active chiral Pd-H species was generated from the proton of alcohols by activating of tetrahydroxydiboron, hydrogen transfer was the rate-determining step, and the reaction preferred Pd(0)-catalyzed mechanism. [Figure not available: see fulltext.]
Asymmetric Transfer Hydrogenation of N-Unprotected Indoles with Ammonia Borane
Zhao, Weiwei,Zhang, Zijia,Feng, Xiangqing,Yang, Jing,Du, Haifeng
supporting information, p. 5850 - 5854 (2020/08/05)
A metal-free asymmetric transfer hydrogenation of unprotected indoles was successfully realized using a catalyst derived from HB(C6F5)2 and (S)-tert-butylsulfinamide with ammonia borane as a hydrogen source. A variety of indolines were achieved in 40-78percent yields with up to 90percent ee.
Dearomatization-Rearomatization Strategy for Synthesizing Carbazoles with 2,2′-Biphenols and Ammonia by Dual C(Ar)-OH Bond Cleavages
Cao, Dawei,Yu, Jing,Zeng, Huiying,Li, Chao-Jun
, p. 13200 - 13205 (2020/12/18)
Carbazole is an essential building block in various pharmaceuticals, agrochemicals, natural products, and materials. For future sustainability, it is highly desirable to synthesize carbazole derivatives directly from renewable resources or cheap raw materials. Phenolic compounds are a class of degradation products of lignin. On the other hand, ammonia is a very cheap industrial inorganic chemical. Herein, an efficient dearomatization-rearomatization strategy has been developed to directly cross-couple 2,2′-biphenols with ammonia by dual C(Ar)-OH bond cleavages. This strategy provides a greener pathway to synthesize valuable carbazole derivatives from phenols.
Br?nsted-Acid-Promoted Rh-Catalyzed Asymmetric Hydrogenation of N-Unprotected Indoles: A Cocatalysis of Transition Metal and Anion Binding
Wen, Jialin,Fan, Xiangru,Tan, Renchang,Chien, Hui-Chun,Zhou, Qinghai,Chung, Lung Wa,Zhang, Xumu
, p. 2143 - 2147 (2018/04/30)
The incorporation of Br?nsted acid, thiourea anion binding, and transition metal catalysis enables an efficient method to synthesize chiral indolines via hydrogenation of indoles. Catalyzed by a rhodium/ZhaoPhos complex, asymmetric hydrogenation of unprotected indoles is performed smoothly with excellent enantioselectivities (up to 99% ee, up to 400 TON). Br?nsted acid HCl activates indoles to form iminium ion intermediates. Mechanistic studies support the assumption that anion binding plays a crucial role as a secondary interaction. DFT calculations reveal an outer-sphere mechanism in this chemical transformation.
Iron-Catalyzed Intramolecular Aminations of C(sp3)?H Bonds in Alkylaryl Azides
Alt, Isabel T.,Guttroff, Claudia,Plietker, Bernd
, p. 10582 - 10586 (2017/08/22)
The nucleophilic iron complex Bu4N[Fe(CO)3(NO)] (TBA[Fe]) catalyzes the direct intramolecular amination of unactivated C(sp3)?H bonds in alkylaryl azides, which results in the formation of substituted indoline and tetrahydroquinoline derivatives.
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.
Indoline derivatives a series of structure containing asymmetric squaraine cyanine small molecule and its application
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Paragraph 0055-0056; 0059-0060, (2019/02/02)
The invention provides a series of novel asymmetric squarine micromolecules, and an application thereof. By introducing different electricity-rich aromatic units in two ends of a squaric acid four-membered ring as donor units, a series of low narrow-gap asymmetric squarine micromolecule photovoltaic materials are designed and synthesized. The series of the low narrow-gap asymmetric squarine micromolecule photovoltaic materials have strong absorption in visible and near-infrared light regions; absorption spectra cover400-900 nm; and HOMO and LUMO of the series of the low narrow-gap asymmetric squarine micromolecule photovoltaic materials can match well with energy levels of an acceptor material PCBM to obtain a high open-circuit voltage. The compounds have good solubility and film-forming property, so that the compounds can be applied in bulk hetero-junction organic solar cells processed by low-cost solution. Performances of the organic solar cells with asymmetric squaric acid macromolecules as donor materials can reach an open-circuit voltage Voc=0.72-1.05 V, a short-circuit current Jsc=8.80-12.67 mA/cm, a fill factor (FF)=0.38-0.55, and photoelectric conversion efficiency (PCE)=2.41-6.10%.
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.
Asymmetric hydrogenation of unprotected indoles using iridium complexes derived from P-OP ligands and (reusable) Bronsted acids
Nunez-Rico, Jose Luis,Fernandez-Perez, Hector,Vidal-Ferran, Anton
, p. 1153 - 1157 (2014/03/21)
Unprotected indoles have been efficiently converted to enantiomerically enriched indolines (up to 91% ee) by a stepwise process: (reusable) Bronsted acid-mediated C=C isomerisation and asymmetric hydrogenation using enantioselective iridium catalysts derived from P-OP ligands. This straightforward combination of (reusable) Bronsted acids, which activate the indole ring for hydrogenation by breaking its aromaticity, and enantiomerically pure [Ir(P-OP)]+ complexes as hydrogenation catalysts affords the resulting indolines with high enantioselectivities.
Chiral phosphoric acid-catalyzed oxidative kinetic resolution of indolines based on transfer hydrogenation to imines
Saito, Kodai,Shibata, Yukihiro,Yamanaka, Masahiro,Akiyama, Takahiko
supporting information, p. 11740 - 11743 (2013/09/02)
The oxidative kinetic resolution of 2-substituted indoline derivatives was achieved by hydrogen transfer to imines by means of a chiral phosphoric acid catalyst. The oxidative kinetic resolution was applicable to racemic alkyl- or aryl-substituted indolines, and the remaining indolines were obtained in good yields with excellent enantioselectivities.
