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1997 Fiscal Year Final Research Report Summary

Asymmetric Protonation of Enolates with Optically Active Imides as Proton Sources

Research Project

Project/Area Number 08455423
Research Category

Grant-in-Aid for Scientific Research (B)

Allocation TypeSingle-year Grants
Section一般
Research Field Synthetic chemistry
Research InstitutionNagoya University

Principal Investigator

YANAGISAWA Akira  Nagoya University School of Engineering, Associate Professor, 工学研究科, 助教授 (60183117)

Project Period (FY) 1996 – 1997
KeywordsAsymmetric Protonation / Optically Active Imide / Enantioselectivity / Enolates / Protonating Agent / Kemp's Tricarboxylic Acid / 2-Oxazoline / 2-Alkylcycloalkanone
Research Abstract

Asymmetric protonation of prochiral metal enolates is an effective route to optically active carbonyl compounds. Although a number of groups have made important contributions to the continuing progress in this process, most of these are the reactions of enolates having polar groups including amino, hydroxyl, or phenyl groups, and there have been few satisfactory reports on the asymmetric induction of enolates of simple ketones such as 2-methylcyclohexanone. We have already reported that the new chiral proton source, (S,S) -or (R,R) -imide, which possesses an asymmetric 2-oxazoline ring, can be easily prepared from Kemp's tricarboxylic acid and (1R,2S) -or (1S,2R) -2-amino-1,2-diphenylethanol, and protonates various lithium enolates of alpha-monoalkylatedcycloalkanones with excellent to moderate enantioselectivity.
In this research, we further examined the asymmetric protonation of simple prochiral metal enolates with the chiral imide and related imides. An increase in enantioselectivity … More was observed in the asymmetric protonation of prochiral lithium enolates with (S,S) -imide using lithium salt as an additive. For example, (R) -enriched 2-n-pentylcyclopentanone was obtained in a nearly quantitative yield with 90% ee when the corresponding lithium enolate was generated in the presence of 5 equiv of LiBr in Et_2O and was protonated with (S,S) -imide in THF.Higher enantioselectivity was observed for the reaction of lithium enolate of 2-methylcyclohexanone with optically active 1-cyclohexylethylamine derived (S) -or (R) -imide, which possesses a chiral amide group, than with (S,S) - or (R,R) -imide. Noteworthy was the fact that the enantioselectivity was highly dependent on the steric bulkiness of alkyl substituents of cyclohexane ring of the imide. These chiral imides were further successfully applied to a diastereoselective protonation of a chiral enolate. When the lithium enolate of (-) -menthone was protonated by (S,S) -imide or (R) -imide, cis-ketone was the major product formed. In contrast, a high trans-selectivity was obtained for the reaction with (R,R) -imide or (S) -imide. The catalytic process of this diastereoselective protonation has been realized using a catalytic amount of these chiral imides and stoichiometric amount of an achiral proton source. Less

  • Research Products

    (12 results)

All Other

All Publications (12 results)

  • [Publications] A.Yanagisawa: "Asymmetric Protonations of Enol Derivatives" Synlett. 411-420 (1997)

    • Description
      「研究成果報告書概要(和文)」より
  • [Publications] 菊地 哲雄: "エノラート類の触媒的不斉プロトン化反応" 化学. 52・6. 68-69 (1997)

    • Description
      「研究成果報告書概要(和文)」より
  • [Publications] A.Yanagisawa: "Diastereoselective Protonation of Chiral Enolate with Chiral Imides" Synlett. 956-958 (1997)

    • Description
      「研究成果報告書概要(和文)」より
  • [Publications] A.Yanagisawa: "Effects of Lithium Salts on the Enantioselectivity of Protonation of Enolates with Chiral Imide" Synlett. (印刷中).

    • Description
      「研究成果報告書概要(和文)」より
  • [Publications] A.Yanagisawa: "Enantioselective Protonation of Prochiral Enolates with Chiral Imides" Tetrahedron. (印刷中).

    • Description
      「研究成果報告書概要(和文)」より
  • [Publications] A.Yanagisawa: "Comprehensive Asymmetric Catalysis" Springer (印刷中),

    • Description
      「研究成果報告書概要(和文)」より
  • [Publications] A.Yanagisawa et al: "Asymmetric Protonations of Enol Derivatives" Synlett. 411-420 (1997)

    • Description
      「研究成果報告書概要(欧文)」より
  • [Publications] T.Kikuchi et al: "Catalytic Asymmetric Protonations of Enolates" Kagaku. 52 (6). 68-69 (1997)

    • Description
      「研究成果報告書概要(欧文)」より
  • [Publications] A.Yanagisawa et al: "Diastereoselective Protonation of Chiral Enolate with Chiral Imides" Synlett. 956-958 (1997)

    • Description
      「研究成果報告書概要(欧文)」より
  • [Publications] A.Yanagisawa et al: "Effects of Lithium Salts on the Enantioselectivity of Protonation of Enolates with Chiral Imide" Synlett. (in press).

    • Description
      「研究成果報告書概要(欧文)」より
  • [Publications] A.Yanagisawa et al: "Enantioselective Protonation of Prochiral Enolates with Chiral Imides" Tetrahedron. (in press).

    • Description
      「研究成果報告書概要(欧文)」より
  • [Publications] A.Yanagisawa et al: Comprehensive Asymmetric Catalysis. Springer (in press),

    • Description
      「研究成果報告書概要(欧文)」より

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Published: 1999-03-16  

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