2005 Fiscal Year Final Research Report Summary
Development of New Catalytic Asymmetric Reactions Based on the Synthesis of Optically Active Phosphine Ligands
| Project/Area Number |
16350020
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| Research Category |
Grant-in-Aid for Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Organic chemistry
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| Research Institution | Chiba University |
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Principal Investigator |
IMAMOTO Tsuneo Chiba University, Faculty of Science, Professor, 理学部, 教授 (10134347)
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| Co-Investigator(Kenkyū-buntansha) |
YOSHIDA Kazuhiro Chiba University, Faculty of Science, Research Associate, 理学部, 助手 (60375607)
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| Project Period (FY) |
2004 – 2005
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| Keywords | Asymmetric Hydrogenation / Optically Active Phosphine / Iridium Complex / Rhodium Complex / Phosphine / P-Chiral Phosphine / Chiral Ligands / Asymmetric Catalysis |
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| Research Abstract |
This study is directed toward the development of new catalytic asymmetric reactions based on the design and synthesis of novel chiral phosphine ligands. A new tetraphosphine ligand bearing their four chiral centers at phosphorus atoms has been synthesized via phosphine-boranes as the intermediates and the molecular structure of its dirhodium complex was determined by the single crystal X-ray analysis. The tetraphosphine lidand itself is C_2 symmetric, but each Rh-diphosphine sphere forms a C_1 symmetric three-hindered quadrant. This dirhodium complex exhibited excellent enantioinduction ability in Rh-catalyzed asymmetric hydrogenation of dehydroamino acids. Low temperature hydrogenation of the complex afforded a tetrahydrorhodium complex quantitatively, and the reactions of the tetrahydride complex with alkene substrates were studied in order to elucidate the detailed enantioselection mechanism. The results including the stereochemical outcome are reasonably interpreted by assuming tha
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t the enantioselection would be determined at the migratory insertion step.
A new P-chiral phosphinophenol was prepared and employed in copper-catalyzed asymmetric conjugate addition to α,β-unsaturated carbonyl compounds. The reactions proceeded smoothly under mild conditions to afford the corresponding products with high enantiomeric excesses of up to 96%.
Asymmetric hydrosilylation of simple ketones was tested by the use of several P-chiral phosphine ligands prepared in our laboratory. Very high enantioselectivity of up to 99% was observed when a bulky silylation reagent such as α-naphtyldiphenylsilane was used. The sense of the stereoselection has been rationalized by considering that the enantioselection occurs at the migratory insertion step.
A new P-chiral diphosphine ligand, (R,R)-2,3-bis(tert-butylmethylphosphino)quinoxaline (QuinoxP^*)) was designed and synthesized by reacting enantiomerically pure (R)-tert-butyl(hydroxymethyl)methylphosphine-borane with 2,3-dichloroquinoxaline. This ligand, in contrast to most of the previously reported P-chiral ligands, is an air-stable solid and exhibits excellent enantioselectivities in both Rh-catalyzed asymmetric hydrogenations and Rh- or Pd-catalyzed carbon-carbon bond-forming reactions. Less
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[Journal Article] P-Chiral Tetraphosphine Dirhodium Complex as a Catalyst for Asymmetric Hydrogenation : Synthesis, Structure, Enantioselectivity, and Mechanism. Stereoselective Formation of a Dirhodium Tetrahydride Complex and Its Reaction with Methyl (Z)-α-Acetamidocinnamate,2006
Author(s)
Imamoto, T., Yashio, K., Crepy, K.V.L., Katagiri, K., Takahashi, H., Kouchi, M., Gridnev, I.D.
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Journal Title
Organometallics 25
Pages: 908-914
Description
「研究成果報告書概要(欧文)」より
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[Journal Article] Highly Enantioselective Hydrosilylation of Simple Ketones Catalyzed by Rhodium Complexes of P-Chiral Diphosphine Ligands Bearing tert-Butylmethyrphosphino Groups,2006
Author(s)
Imamoto, T., Itoh, T., Yamanoi, Y., Narui, R., Yoshida, K.
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Journal Title
Tetrahedron : Asymmetry 17
Pages: 560-565
Description
「研究成果報告書概要(欧文)」より
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[Journal Article] P-Chiral o-Phosphinophenol as a P/O Hybrid Ligand : Preparation and Use in Cu-Catalyzed Asymmetric Conjugate Addition of Diethylzinc to Acyclic Enones,2005
Author(s)
Takahashi, Y., Yamamoto, Y., Katagiri, K., Danjo, K., Yamaguchi, K., Imamoto, T.
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Journal Title
J.Org.Chem. 70
Pages: 9009-9012
Description
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[Journal Article] Preparation of (S,S)-Bis(tert-butylmethylphosphino)ethane ((S,S)-t-Bu-BisP^*) as a Rhodium Complex,.2005
Author(s)
Crepy, K.V.L., Imamoto, T., Seidel, G., Furstner, A.
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Journal Title
Organic Syntheses 82
Pages: 22-29
Description
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[Journal Article] Dihydroboronium Derivative of (S,S)-1,2-Bis(t-butylmethylphosphino)ethane as Convenient Chiral Ligand Precursors,2004
Author(s)
Miyazaki, T., Sugawara, M., Danjo, H., Imamoto, T.
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Journal Title
Tetrahedron Lett. 45
Pages: 9341-9344
Description
「研究成果報告書概要(欧文)」より
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[Journal Article] Optically Pure 1,2-[Bis(o-alkylphenyl)phenylphosphino]ethanes and Their Use in Rhodium-Catalyzed Asymmetric Hydrogenations of α-(Acylamino)acrylic Derivatives,2004
Author(s)
Wada, Y., Imamoto, T., Tsuruta, H., Yamaguchi, K., Gridnev, I.D.
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Journal Title
Adv.Syn.Catal. 346
Pages: 777-788
Description
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