Bulletin of the Korean Chemical Society

Korean Chemical Society (대한화학회)
권호 표지
DOI QR코드

DOI QR Code

New Chiral Borohydrides. 2. Preparation of Potassium B-Methoxydiisopinocampheylborohydride and Its Asymmetric Reducing Properties

  • Published : 1991.12.20
Download PDF
⟨ Previous Next ⟩

Abstract

In order to prepare new chiral borohydrides (4) possessing chirality on dialkyl moieties, a series of B-alkoxydiisopinocampheylborinates (3) were synthesized by treatment of diisopinocampheylborane ($Ipc_2BH$) with alcohols (R in ROH: Me, Et, i-Pr, t-Bu) and reacted with excess of potassium hydride. Of these chiral borinic esters, only B-methoxydiisopinocampheyl borinate (3a) was converted into the corresponding dialkylmonoalkoxyborohydride (4a). For the other borinic esters, hydride uptake reactions were very slow at room temperature, accompanying disproportionation products at $65^{\circ}C$. The hydride (4a) formed is stable at $0^{\circ}C$ and can be stored over potassium hydride for few months. In the asymmetric reduction of the selected ketones, 4a provided the corresponding alcohols, such as 21% ee for 3-methyl-2-butanone, 11% ee for 2,2-dimethylcyclopentanone, 24% ee for acetophenone, 32% ee for 3-acetylpyridine, 30% for methyl benzoylformate, 31% ee for 4-phenyl-3-butyn-2-one, 39% ee for 3-butyn-2-one, and 34% ee for 3-hexyn-2-one.

Keywords

References

  1. J. Korean. Chem. Soc. v.34 B. T. Cho
  2. J. Org. Chem. v.51 H. C. Brown;W. S. Park;B. T. Cho
  3. Bull. Korean Chem. Soc. v.8 W. S. Park;B. T. Cho;J. S. Cha
  4. Bull. Korean Chem. Soc. v.8 H. C. Brown;W. S. Park;B. T. Cho
  5. J. Org. Chem. v.53 H. C. Brown;B. T. Cho;W. S. Park
  6. J. Org. Chem. v.51 H. C. Brown;W. S. Park;B. T. Cho
  7. J. Org. Chem. v.51 H. C. Brown;B. T. Cho;W. S. Park
  8. Bull. Korean Chem. Soc. v.8 B. T. Cho;W. S. Park
  9. J. Org. Chem. v.49 H. C. Brown;B. Singaram
  10. Tetrahedron v.37 H. C. Brown; P. K. Jadhav;A. K. Mandal
  11. Chemtec. v.15 H. C. Brown;B. Singaram
  12. Modern Synthetic Methods 1986 v.4 H. C. Brown;P. K. Jadhav;B. Singaram;R. Scheffold(ed.)
  13. Aldrichim. Acta v.20 M. Srebnik;P. V. Ramachandran
  14. Acc. Chem. Res. v.21 H. C. Brown;B. Singaram
  15. J. Org. Chem. v.50 H. C. Brown;J. S. Cha;B. Nazer;C. A. Brown
  16. J. Org. Chem. v.34 MTPA=${\alpha}$-methoxy-${\alpha}$-(trifluoromethyl) phenylacetic acid J. A. Dale;D. A. Dull;H. S. Mosher
  17. J. Org. Chem. v.33 J. W. Westly;B. Halpern
  18. J. Org. Chem. v.50 P. K. Jadhav;J. V. N. Vara Prasad;H. C. Brown
  19. Organic Synthesis via Boranes H. C. Brown;G. W. Kramer;A. B. Levy;M. M. Midland