• Title/Summary/Keyword: Asymmetric reactions

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Regulation of Stereoselectivity and Reactivity in the Inter- and Intramolecular Allylic Transfer Reactions

  • Yu, Chan-Mo;Youn, Jin-soup;Jung, Hee-Keum
    • Bulletin of the Korean Chemical Society
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    • v.27 no.4
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    • pp.463-472
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    • 2006

  • The preparation of enatiomerically enriched homoallylic alcohols through asymmetric addition of chiral allylic transfer reagents and allylating reagents with chiral catalysts to the carbonyl functionalities represents an important chemical transformation. Excellent progress has been made over past decade in the development and application of catalytic asymmetric allylic transfer reactions. In this account, our efforts for the various intermolecular allylic transfer reactions such as allylation, propargylation, allenylation, and dienylation utilizing accelerating strategy and sequential allylic transfer reactions to achieve multiple stereoselection mainly using transition metal catalysts are described.

  • https://doi.org/10.5012/bkcs.2006.27.4.463 인용 PDF KSCI

Biomimetic Catalysis in Ionic Liquids: Markedly Enhanced Enantioselectivity in Amino Acid-Catalyzed Directed Asymmetric Aldol Reactions

  • Yun, Suk-Jin;Lee, Jae Kwan
    • Journal of Integrative Natural Science
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    • v.8 no.2
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    • pp.107-110
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    • 2015

  • Amino acid-catalyzed directed asymmetric aldol reactions showed enhanced enantioselectivity when conducted in ionic liquids. Optically active products were afforded in better yields (up to 23% higher) and enantiomeric excess (up to 21% higher) in ionic liquids than in conventional organic solvents.

  • https://doi.org/10.13160/ricns.2015.8.2.107 인용 PDF KSCI

Chiral Mesoporous Silica for Asymmetric Metal-free Catalysis: Enhancement of Chirality thorough Confinement Space by Plug Effect

  • Jeong, Eun-Yeong;Im, Cheong-Rae;Park, Sang-Eon
    • Proceedings of the Korean Vacuum Society Conference
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    • 2011.08a
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    • pp.199-199
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    • 2011

  • The addition of a carbanion to ${\yen}{\acute{a}}{\yen}{\hat{a}}$-unsaturated carbonyl compounds is of importance in the C-C bond formation reactions for modern pharmaceuticals and organic synthesis. Recently, heterogeneous asymmetric catalysis became more attractive area of research because of the easy recovery and separation of the catalyst from the reaction system. Most of synthetic methods for heterogeneous catalysts were grafting or immobilization of homogeneous catalyst onto the solid supports. Trans-1,2-Diaminocyclohexane(DACH) and L-proline ligands have been enormously used as chiral ligands in several catalytic transformation under homogenous conditions. Our group prepared l-proline functionalized mesoporous silica was synthesized under acidic condition using a poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) triblock copolymer template (EO20PO70EO20, Pluronic P-123, BASF). Furthermore, we successfully directly synthesized trans-1,2 diaminocyclohexane functionalized mesoporous silica by using microwave method. The direct functionalization of chiral ligand into the framework of mesoporous materials is expected to be useful for the heterogeneous asymmetric catalysis. So, we adopt the direct synthesis of chiral ligand functionalized mesoporous silica by using thermal and microwave irradiation. Then, chiral ligand functionalized mesoporous silicas were applied to enantioselective asymmetric catalytic reactions.

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Design, Synthesis and Catalytic Property of L-Proline Derivatives as Organocatalysts for Direct Aldol Reaction

  • Wang, Lei;Tang, Ruiren;Yang, Hua
    • Journal of the Korean Chemical Society
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    • v.57 no.5
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    • pp.591-598
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    • 2013

  • A series of chiral prolinamide compounds with pyridine-2, 6-dicarboxylic acid moieties derived from L-proline have been designed and synthesized, their catalytic properties for direct asymmetric aldol reactions were also studied in this article. These catalysts gave the aldol product in high yield (87%) and high enantioselectivity, up to 85%, of the anti-structure at room temperature but gave disappointing results at a lower temperature or when additive was added. Conditions, including solvents, temperature and additives were screened for the reactions. Moreover, the influence of presence of water on yield and stereoselectivity was also discussed.

  • https://doi.org/10.5012/jkcs.2013.57.5.591 인용 PDF KSCI KPUBS HTML