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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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shedding light on bronsted Acid Catalysis a photocyclization reduction reaction for the asymmetric synthesis of tetrahydroquinolines from aminochalcones in batch and flow
Chemical Communications, 2013Co-Authors: Hsuanhung Liao, Chienchi Hsiao, Erli Sugiono, Magnus RuepingAbstract:A new asymmetric photocyclization–reduction cascade employing readily available aminochalcones has been developed. The reaction sequence has been achieved by unifying photochemistry and asymmetric Bronsted Acid Catalysis and involves photocyclization followed by Bronsted Acid catalyzed enantioselective hydrogenation in batch and flow.
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merging visible light photoredox and lewis Acid Catalysis for the functionalization and arylation of glycine derivatives and peptides
Chemical Communications, 2012Co-Authors: Shaoqun Zhu, Magnus RuepingAbstract:A relay Catalysis protocol for the functionalization of α-amino Acids and dipeptides using a combination of visible-light photoredox and Lewis Acid Catalysis has been developed.
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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.
Hong Wang - One of the best experts on this subject based on the ideXlab platform.
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trio Catalysis merging enamine broensted Acid and metal lewis Acid Catalysis asymmetric three component aza diels alder reaction of substituted cinnamaldehydes cyclic ketones and arylamines
ChemInform, 2015Co-Authors: Yongming Deng, Siddhartha Kumar, Kraig A Wheeler, Hong WangAbstract:A trio catalyst system composed of arylamine, BINOL-derived phosphoric Acid, and Y(OTf)3, enables the combination of enamine Catalysis with both hard metal Lewis Acid Catalysis and Broensted Acid Catalysis for the first time.
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trio Catalysis merging enamine bronsted Acid and metal lewis Acid Catalysis asymmetric three component aza diels alder reaction of substituted cinnamaldehydes cyclic ketones and arylamines
Chemistry: A European Journal, 2015Co-Authors: Yongming Deng, Siddhartha Kumar, Kraig A Wheeler, Hong WangAbstract:A trio catalyst system, composed of arylamine, BINOL-derived phosphoric Acid, and Y(OTf)3, enables the combination of enamine Catalysis with both hard metal Lewis Acid Catalysis and Bronsted Acid Catalysis for the first time. Using this catalyst system, a three-component aza-Diels–Alder reaction of substituted cinnamaldehyde, cyclic ketone, and arylamine is carried out with high chemo- and enantioselectivity, affording a series of optically active 1,4-dihydropyridine (DHP) derivatives are obtained in 91–99 % ee and 59–84 % yield. DHPs bearing a chiral quaternary carbon center are also obtained with good enantioselectivity and moderate yield (three examples). Preliminary mechanistic investigations have also been conducted.
Dennis G. Hall - One of the best experts on this subject based on the ideXlab platform.
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Boronic Acid Catalysis.
Chemical Society reviews, 2019Co-Authors: Dennis G. HallAbstract:Although boronic Acids are recognized primarily for their utility as reagents in transition metal-catalyzed transformations, other applications are emerging, including their use as reaction catalysts. Few methods are available for the catalytic activation of hydroxy functional groups as a way to promote their direct transformation into useful products under mild conditions. To this end, the ability of boronic Acids to form reversible covalent bonds with hydroxy groups can be exploited to enable both electrophilic and nucleophilic modes of activation in various organic reactions. Using the concept of boronic Acid Catalysis (BAC), electrophilic activation of carboxylic Acids leads to the formation of amides from amines, as well as cycloadditions and conjugate additions with unsaturated carboxylic Acids. Alcohols can also be activated with boronic Acid catalysts to form carbocation intermediates that can be trapped in selective Friedel–Crafts-type reactions with arenes and other nucleophiles. On the other hand, diols and saccharides can form tetrahedral adducts with boronic Acids, which increases their nucleophilic character towards electrophiles. Altogether, BAC imparts mild and selective reaction conditions that display high atom-economy by circumventing the need for wasteful stoichiometric activation of hydroxy groups into halides or sulfonates.
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boronic Acid Catalysis for mild and selective 3 2 dipolar cycloadditions to unsaturated carboxylic Acids
ChemInform, 2010Co-Authors: Hongchao Zheng, Robert Mcdonald, Dennis G. HallAbstract:Free, unsaturated carboxylic Acids can participate directly in dipolar cycloadditions with azides, nitrile oxides, and nitrones by using mild boronic Acid Catalysis at room temperature to give readily isolated heterocyclic products.
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boronic Acid Catalysis for mild and selective 3 2 dipolar cycloadditions to unsaturated carboxylic Acids
Chemistry: A European Journal, 2010Co-Authors: Hongchao Zheng, Robert Mcdonald, Dennis G. HallAbstract:Herein, the concept of boronic Acid Catalysis (BAC) for the activation of unsaturated carboxylic Acids is applied in several classic dipolar [3+2] cycloadditions involving azides, nitrile oxides, and nitrones as partners. These cycloadditions can be used to produce pharmaceutically interesting, small heterocyclic products, such as triazoles, isoxazoles, and isoxazolidines. These cycloadducts are formed directly and include a free carboxylic Acid functionality that can be employed for further transformations, thereby avoiding prior masking or functionalization. In all cases, BAC provides faster reactions, under milder conditions, with much improved product yields and regioselectivities. In some instances, such as triazole formation from the reaction of azides with 2-alkynoic Acids, Catalysis with ortho-nitrophenylboronic Acid circumvents the undesirable product decarboxylation observed when using thermal activation. By using NMR spectroscopic studies, the boronic Acid catalyst was shown to provide activation by a LUMO-lowering effect in the unsaturated carboxylic Acid, likely via a monoacylated hemiboronic ester intermediate.
Masahiro Terada - One of the best experts on this subject based on the ideXlab platform.
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secondary stereocontrolling interactions in chiral bronsted Acid Catalysis study of a petasis ferrier type rearrangement catalyzed by chiral phosphoric Acids
Chemical Science, 2014Co-Authors: Kyohei Kanomata, Yasunori Toda, Yukihiro Shibata, Masahiro Yamanaka, Seiji Tsuzuki, Ilya D Gridnev, Masahiro TeradaAbstract:Chiral phosphoric Acids have emerged as promising asymmetric Bronsted Acid catalysts that harness hydrogen bonding interactions as key stereocontrolling elements. A new approach to chiral phosphoric Acid Catalysis through ion-pairing interactions between the anionic conjugate base of the catalyst and a cationic electrophile has recently attracted attention. However, the mechanism of stereocontrol through ion-pairing interactions is still elusive. As a probe reaction for studying the stereocontrolling element involved in such catalytic reactions, we investigated the Petasis–Ferrier-type rearrangement of a 7-membered cyclic vinyl acetal catalyzed by chiral phosphoric Acids. DFT calculations suggested that non-classical C–H⋯O hydrogen bonds between the catalyst and the substrate play an important role in determining the stereoselectivity. In addition, π–π stacking interactions were found to be a key factor for stereocontrol when using a 9-anthryl group-bearing catalyst.
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chiral bronsted Acid Catalysis for enantioselective hosomi sakurai reaction of imines with allyltrimethylsilane
Organic Letters, 2011Co-Authors: Norie Momiyama, Hayato Nishimoto, Masahiro TeradaAbstract:The chiral Bronsted Acid (1b or 1c) has been shown to initiate the Hosomi−Sakurai reaction of imines with excellent enantioselectivities. The combined Bronsted Acid system has been developed to offer a new class of chiral Bronsted Acid Catalysis. The present system proceeds through regeneration of the chiral Bronsted Acid by proton transfer from additional Bronsted Acid to silylated chiral Bronsted Acid, a newly elucidated mechanism for the role of the additional Bronsted Acid.
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chiral phosphoric Acids as versatile catalysts for enantioselective carbon carbon bond forming reactions
ChemInform, 2010Co-Authors: Masahiro TeradaAbstract:An inventive approach to the development of chiral Bronsted Acid Catalysis, to enable catalysts which possess strong Acid functionalities, has been accomplished. Among the various organic Bronsted ...
Keiji Maruoka - One of the best experts on this subject based on the ideXlab platform.
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boronic Acid catalyzed highly enantioselective aza michael additions of hydroxamic Acid to quinone imine ketals
Journal of the American Chemical Society, 2015Co-Authors: Takuya Hashimoto, Alberto Osuna Galvez, Keiji MaruokaAbstract:Boronic Acid is one of the most versatile organic molecules in chemistry. Its uses include organic reactions, molecular recognition, assembly, and even medicine. While boronic Acid Catalysis, which utilizes an inherent catalytic property, has become an important research objective, it still lags far behind other boronic Acid chemistries. Here, we report our discovery of a new boronic Acid Catalysis that enables the aza-Michael addition of hydroxamic Acid to quinone imine ketals. By using 3-borono-BINOL as a chiral boronic Acid catalyst, this reaction could be implemented in a highly enantioselective manner, paving the way to densely functionalized cyclohexanes.
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Boronic Acid-Catalyzed, Highly Enantioselective Aza-Michael Additions of Hydroxamic Acid to Quinone Imine Ketals
2015Co-Authors: Takuya Hashimoto, Alberto Osuna Gálvez, Keiji MaruokaAbstract:Boronic Acid is one of the most versatile organic molecules in chemistry. Its uses include organic reactions, molecular recognition, assembly, and even medicine. While boronic Acid Catalysis, which utilizes an inherent catalytic property, has become an important research objective, it still lags far behind other boronic Acid chemistries. Here, we report our discovery of a new boronic Acid Catalysis that enables the aza-Michael addition of hydroxamic Acid to quinone imine ketals. By using 3-borono-BINOL as a chiral boronic Acid catalyst, this reaction could be implemented in a highly enantioselective manner, paving the way to densely functionalized cyclohexanes
