The Experts below are selected from a list of 27771 Experts worldwide ranked by ideXlab platform
Magnus Rueping - One of the best experts on this subject based on the ideXlab platform.
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enantio and diastereoselective access to distant stereocenters embedded within tetrahydroxanthenes utilizing ortho quinone methides as reactive intermediates in asymmetric Bronsted Acid catalysis
Angewandte Chemie, 2014Co-Authors: Chienchi Hsiao, Hsuanhung Liao, Magnus RuepingAbstract:A protocol for the highly enantioselective synthesis of 9-substituted tetrahydroxanthenones by means of asymmet- ric Bronsted Acid catalysis has been developed. A chiral binol- based N-triflyphosphoramide was found to promote the in situ generation of ortho-quinone methides and their subsequent reaction with 1,3-cyclohexanedione to provide the desired products with excellent enantioselectivities. In addition, a highly enantio- and diastereoselective Bronsted Acid cata- lyzed desymmetrization of 5-monosubstituted 1,3-dicarbonyl substrates with ortho-quinone methides gives rise to valuable tetrahydroxanthenes containing two distant stereocenters.
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asymmetric Bronsted Acid catalysis in aqueous solution
Chemical Science, 2010Co-Authors: Magnus Rueping, Thomas TheissmannAbstract:A biologically inspired reaction design leads to the development of the first highly enantioselective Bronsted Acid catalysed reaction in aqueous solution.
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unifying metal and Bronsted Acid catalysis concepts mechanisms and classifications
Chemistry: A European Journal, 2010Co-Authors: Magnus Rueping, Rene M Koenigs, Iuliana AtodireseiAbstract:Asymmetric catalysis is a key feature of modern synthetic organic chemistry. Traditionally, different combinations of ligands and metals are used to perform highly enantioselective reactions. Since the renaissance of organocatalysis in the early 2000s, tremendous improvement in the field of metal-free catalysis has been achieved. Recently, the combination of transition metals and organocatalysts has allowed the development of new protocols enabling transformations that could not previously be realized. This article aims to present the latest contributions in the field of combined chiral Bronsted Acid and metal catalyzed reactions, highlighting the advantages of these catalytic systems as well as describing the uncertainties regarding the molecular structure of the catalytically active species and the reaction mechanisms.
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thieme chemistry journal awardees where are they now asymmetric Bronsted Acid catalyzed transfer hydrogenations
Synlett, 2010Co-Authors: Magnus Rueping, Erli Sugiono, Fenja R. SchoepkeAbstract:Asymmetric hydrogenations are of great importance in the synthesisof optically active amines. This account highlights the developmentof the first metal-free transfer hydrogenation that is both highlyenantioselective and inspired by nature’s dehydrogen-ase.Further focus is given to the extension of this bioinspired processto provide a variety of valuable, biologically active products andnatural products under mild reaction conditions. 1 Introduction 2 Nature’s Reductions: Dehydrogenases as a Role Model 3 Bronsted Acid catalyzed Transfer Hydrogenation of Ketimines 4 Asymmetric Organocatalytic Reduction of Quinolines 5 Asymmetric Organocatalytic Reduction of N-Heterocycles 5.1 Asymmetric Bronsted Acid Catalyzed Hydrogenationof -Indoles 5.2 Asymmetric Bronsted Acid Catalyzed Hydrogenationof Benzoxazines, Benzthiazines, Benzoxazinones, Quinoxalines, Quinoxalinonesand Benzodiazepinones 6 Asymmetric Organocatalytic Reduction of Pyridines 7 Asymmetric Organocatalytic Reductions in Cascade -Sequences 8 Conclusion
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asymmetric counterion pair catalysis an enantioselective Bronsted Acid catalyzed protonation
Advanced Synthesis & Catalysis, 2008Co-Authors: Magnus Rueping, Thomas Theissmann, Sadiya Raja, Jan W BatsAbstract:A new asymmetric Bronsted Acid-catalyzed cascade reaction involving a 1,4-addition, enantioselective protonation and 1,2-addition has been developed. This organocatalytic cascade not only provides for the first time 3- and 2,3-substituted tetrahydroquinolines and octahydroacridines in good yields with high dia- and enantioselectivities under mild reaction conditions but additionally represents the first example of a chiral Bronsted Acid-catalyzed protonation reaction in an organocatalytic domino reaction. Furthermore, the new Bronsted Acid-catalyzed hydride-proton-hydride transfer cascade can be applied to prepare new molecular scaffolds with up to three new stereocenters in an efficient one-pot reaction sequence.
Liu-zhu Gong - One of the best experts on this subject based on the ideXlab platform.
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Isothiourea and Bronsted Acid Cooperative Catalysis: Enantioselective Construction of Dihydropyridinones.
Organic Letters, 2020Co-Authors: Yu-chen Zhang, Rui-long Geng, Jin Song, Liu-zhu GongAbstract:Asymmetric annulation of bench-stable α,β-unsaturated aryl esters with enamines was realized via cooperative catalysis of chiral isothiourea and Bronsted Acid. This reaction proceeds via a chiral α...
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cascade hydroamination redox reaction for the synthesis of cyclic aminals catalyzed by a combined gold complex and Bronsted Acid
Chemistry: A European Journal, 2013Co-Authors: Yuping He, Dian-feng Chen, Hua Wu, Jie Yu, Liu-zhu GongAbstract:Relay catalysis: An unprecedented protocol for the synthesis of cyclic aminals has been realized under the relay catalysis of a gold(I)/Bronsted Acid binary system to generate cyclic aminals in excellent yields of up to 99 % with moderate to high diastereoselectivity (see scheme; up to 95:5 d.r.).
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Bronsted Acid rhodium ii cooperative catalytic asymmetric three component aldol type reaction for the synthesis of 3 amino oxindoles
Chemistry: A European Journal, 2013Co-Authors: Xiaolei Lian, Liu-zhu GongAbstract:Cooperation is key! Chiral Bronsted Acid/rhodium(II) cooperative catalysis enabled an enantioselective three-component aldol-type reaction of 3-diazo oxindoles and anilines with glyoxylates to give highly functionalized and structurally diverse 3-amino oxindoles in high stereoselectivity (>20:1 d.r., 99 % ee; see scheme).
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consecutive intramolecular hydroamination asymmetric transfer hydrogenation under relay catalysis of an achiral gold complex chiral Bronsted Acid binary system
Journal of the American Chemical Society, 2009Co-Authors: Han Xiao, Xiaohua Chen, Liu-zhu GongAbstract:Consecutive hydroamination/asymmetric transfer hydrogenation under relay catalysis of an achiral gold complex/chiral Bronsted Acid binary system has been described for the direct transformation of 2-(2-propynyl)aniline derivatives into tetrahydroquinolines with high enantiomeric purity.
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cooperative catalysis with chiral Bronsted Acid rh2 oac 4 highly enantioselective three component reactions of diazo compounds with alcohols and imines
Journal of the American Chemical Society, 2008Co-Authors: Wenhao Hu, Xinfang Xu, Jing Zhou, Haoxi Huang, Juan Hu, Liping Yang, Liu-zhu GongAbstract:An asymmetric three-component reaction of diazo compounds and alcohols with imines catalyzed cooperatively by a rhodium complex and a chiral Bronsted Acid provides a general and efficient entry to β-amino-α-hydroxyl Acid derivatives in high yields with excellent stereoselectivities.
Hisashi Yamamoto - One of the best experts on this subject based on the ideXlab platform.
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chiral Bronsted Acid as a true catalyst asymmetric mukaiyama aldol and hosomi sakurai allylation reactions
Journal of the American Chemical Society, 2015Co-Authors: Hisashi YamamotoAbstract:Highly diastereo- and enantioselective Mukaiyama aldol reaction catalyzed by a new chiral Bronsted Acid, N-(perfluorooctanesulfonyl)thiophosphoramide, is described. The perfluorooctyl substituent on the sulfonyl group of the catalyst plays an essential role in the stereoselection. The catalyst also allows the asymmetric Hosomi–Sakurai allylation, which has been considerably challenging due to the low reactivity of allylsilanes. 29Si and 31P NMR monitoring reveals the characteristic feature of the thiophosphoramide catalyst, acting as a strong Bronsted Acid even in the presence of excess silyl nucleophiles, which cannot be found in other related phosphoric Acid analogues.
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super Bronsted Acid catalysis
Chemical Communications, 2011Co-Authors: Cheolhong Cheon, Hisashi YamamotoAbstract:Bronsted Acid catalysis has emerged as a new class of catalysis in modern organic synthesis. However, in order to make the utility of the Bronsted Acid catalysis as broad as the well-developed Lewis Acid catalysis, it is desirable to develop Bronsted Acids demonstrating both high reactivities and selectivities. In this feature article, we will present our achievement in the design and development of strong Bronsted Acids and their application to organic reactions. Furthermore, we will describe the Tf2NH-catalyzed Mukaiyama aldol reaction of super silyl enol ethers. We also will highlight the differences in reactivity and chemo- and stereo-selectivity between Bronsted and Lewis Acid catalysis.
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a Bronsted Acid catalyst for the enantioselective protonation reaction
Journal of the American Chemical Society, 2008Co-Authors: Cheolhong Cheon, Hisashi YamamotoAbstract:A highly reactive and robust chiral Bronsted Acid catalyst, chiral N-triflyl thiophosphoramide, was developed. The first metal-free Bronsted Acid catalyzed enantioselective protonation reaction of silyl enol ethers was demonstrated using this chiral Bronsted Acid catalyst. The catalyst loading could be reduced to 0.05 mol % without any deleterious effect on the enantioselectivity.
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Super Bronsted Acid catalysis in organic synthesis
Chimia, 2007Co-Authors: Hisashi Yamamoto, Matthew B. BoxerAbstract:This mini-review concerns the rapidly growing field of Bronsted Acid catalysis. Bronsted Acid catalysts are able to play an important role in green chemistry. Without the use of any transition metal catalysts, various organic transformations including asymmetric synthesis can be performed efficiently. This review summarizes our recent results in this field.
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design of chiral n triflyl phosphoramide as a strong chiral Bronsted Acid and its application to asymmetric diels alder reaction
Journal of the American Chemical Society, 2006Co-Authors: Daisuke Nakashima, Hisashi YamamotoAbstract:A highly reactive and Acidic chiral Bronsted Acid catalyst, chiral N-triflyl phosphoramide, was developed. Highly enantioselective Diels−Alder reaction of α,β-unsaturated ketone with silyloxydiene was demonstrated using this chiral Bronsted Acid catalyst.
Masahiro Terada - One of the best experts on this subject based on the ideXlab platform.
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relay catalysis by a metal complex Bronsted Acid binary system in a tandem isomerization carbon carbon bond forming sequence
Journal of the American Chemical Society, 2008Co-Authors: Keiichi Sorimachi, Masahiro TeradaAbstract:A one-pot tandem isomerization/carbon−carbon bond forming sequence catalyzed by a ruthenium complex/Bronsted Acid binary system is demonstrated. The method enables the use of readily available allylamides to deliver reactive imines under relay catalysis using a binary catalytic system. Subsequent Bronsted Acid catalyzed carbon−carbon bond forming reactions of the generated imines with nucleophilic components afforded Friedel−Crafts and Mannich products in good yields.
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enantioselective friedel crafts reaction of electron rich alkenes catalyzed by chiral Bronsted Acid
Journal of the American Chemical Society, 2007Co-Authors: Masahiro Terada, Keiichi SorimachiAbstract:We present the first enantioselective catalysis of the Friedel−Crafts reaction via activation of electron-rich multiple bonds by a chiral Bronsted Acid. The reaction of various indole derivatives with a broad range of substituted enecarbamates affords the corresponding Friedel−Crafts products in high yield and enantioselectivity.
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chiral Bronsted Acid catalyzed direct mannich reactions via electrophilic activation
Journal of the American Chemical Society, 2004Co-Authors: Daisuke Uraguchi, Masahiro TeradaAbstract:It was found that the phosphoric Acid derivatives of general structure 1 serve as highly effective catalysts for the direct addition of acetyl acetone to N-Boc-protected arylimines. The beneficial effects of the 3,3‘-bisaryl substituents of the catalysts on the enantioselectivity are greatly appreciated, and thus 1d functions as an excellent catalyst. The Bronsted Acid-catalyzed direct Mannich reactions presented herein provide an attractive way to construct β-aminoketones under extremely mild conditions. The stereochemical course of this reaction was established through the synthesis of Boc-(S)-phenylglycine methylester. The transformation thus demonstrated is applicable to a useful method for the synthesis of various phenylglycine derivatives.
Kohei Fuchibe - One of the best experts on this subject based on the ideXlab platform.
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chiral Bronsted Acid catalyzed enantioselective mannich type reaction
Journal of the American Chemical Society, 2007Co-Authors: Masahiro Yamanaka, Kohei Fuchibe, Junji Itoh, Takahiko AkiyamaAbstract:Mannich-type reaction of ketene silyl acetals with aldimines proceeded catalytically by means of a phosphoric Acid diester, derived from (R)-BINOL, as a chiral Bronsted Acid to afford β-amino esters with good diastereoselectivity in favor of the syn isomer and high enantioselectivity (up to 96% ee). The highest enantioselectivity was achieved by the phosphoric Acid diester bearing 4-nitrophenyl groups on the 3,3‘-positions of BINOL. The N-2-hydroxyphenyl group of aldimine was found to be essential for the present Mannich-type reaction. In combination with these experimental investigations, two possible monocoordination and dicoordination pathways were explored using density functional theory calculations (BHandHLYP/6-31G*). The present reaction proceeds via a dicoordination pathway through the zwitterionic and nine-membered cyclic transition state (TS) consisting of the aldimine and the phosphoric Acid. The re-facial selectivity was also well-rationalized theoretically. The nine-membered cyclic structure ...
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recent progress in chiral Bronsted Acid catalysis
Advanced Synthesis & Catalysis, 2006Co-Authors: Takahiko Akiyama, Junji Itoh, Kohei FuchibeAbstract:Hydrogen bond catalysis and Bronsted Acid catalysis are rapidly growing areas in organocatalysis. A number of chiral Acid catalysts has been developed recently. Recent progress in the chiral Bronsted Acid catalysis has been reviewed with a focus being placed on thiourea, TADDOL, and phosphoric Acids. 1 Introduction 2 Hydrogen Bond Catalysis 2.1 Monofunctional Thiourea Catalysts 2.2 Bifunctional Thiourea Catalysts 2.3 TADDOL Derivatives 2.4 BINOL Derivatives 3 Bronsted Acid Catalysis 3.1 Ammonium Salts 3.2 Phosphoric Acids 4 Conclusion
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chiral Bronsted Acid catalyzed enantioselective hydrophosphonylation of imines asymmetric synthesis of α amino phosphonates
Organic Letters, 2005Co-Authors: Takahiko Akiyama, Hisashi Morita, And Junji Itoh, Kohei FuchibeAbstract:A cyclic phosphoric Acid derivative, derived from (R)-BINOL, was used as a chiral Bronsted Acid (10 mol %) in hydrophosphonylation of aldimines with diisopropyl phosphite at room temperature. α-Amino phosphonates were obtained with good to high enantioselectivities.
