Highly Enantioselective Borane Reduction of Ketones Catalyzed by Chiral Oxazaborolidines. Mechanism and Synthetic Implications

Journal of the American Chemical Society

Volumn 109, Issue 18, 1987, Pages 5551-5553

  Corey, E J ^a   Bakshi, Raman K ^a   Shibata, Saizo ^a  

^a HARVARD UNIVERSITY   (United States)

Author keywords

[No Author keywords available]

Indexed keywords

EID: 33845282886     PISSN: 00027863     EISSN: 15205126     Source Type: Journal    
DOI: 10.1021/ja00252a056     Document Type: Article

References (7)

1. For reviews, see: ApSimon, J. W.; Collier, T. L. Tetrahedron 1986, 42, 5157–5254. Haubenstock, H. Topics Stereochem. 1983, 14, 231–300. Mukaiyama, T.; Asami, M. In Topics in Current Chemistry, No. 127, Organic Chemistry: Springer-Verlag: Berlin. 1985;- pp 133–167.
2. See: Itsuno, S.; Ito, K.; Hirao, A.; Nakahama, S. J. Chem. Soc., Chem. Commun. 1983, 469–470. Itsuno, S.; Ito, K.; Hirao, A.; Nakahama, S. J. Org. Chem. 1984, 49, 555–557. Itsuno, S.; Nakano, M.; Miyazaki, K.; Masuda, H.; Ito, K.; Hirao, A.; Nakahama, S. J. Chem. Soc., Perkin Trans l 1985, 2039–2044. Itsuno, S.; Nakano, M.; Ito, K.; Hirao, A.; Owa, M.; Kanda, N.; Nakahama, S. J. Chem. Soc., Perkin Trans. 1 1985, 2615–2619. Itsuno, S.; Sakurai, Y.; Ito, K.; Hirao, A.; Nakahama, S. Bull. Chem. Soc. Jpn. 1987, 60, 395–396.
3. The observed 11B NMR chemical shift is consistent with structure 2, see: Eaton, G. R.; Lipscomb, W. N., NMR Studies of Boron Hydrides and Related Compounds; W. A. Benjamin: New York, 1969. Noth, H.; Wrackmeyer, B. Nuclear Magnetic Resonance Spectroscopy of Boron Compounds: Springer-Verlag: Berlin, 1978.
4. See: Leach, J. B.; Ungermann, C. B.; Onak, T. P. J. Magn. Reson. 1972, 6, 74–83.
5. Determination of ee values was made by capillary gas chromatographic analysis of the (-)-menthyloxycarbonyl derivatives of the various alcohols obtained by reduction according to Westley and Halpern (Westley, J. W.; Halpern, B. J. Org. Chem. 1968, 33, 3978–3980). Using an OV-1 (or DB-1) silicone column (170 °C) the derivatives of - and -1-phenylethanol, for example, had retention times of 7.32 and 6.91 min, respectively.
6. (S)-Diphenylprolinol was synthesized directly by reaction of N-(ben-zyloxycarbonyl)-(S)-proline methyl ester with phenylmagnesium chloride (8 equiv) in THF initially at 0 °C and then at 23 °C for 16 h; for a previous preparation, see: Kapfhammer, J.; Matthes, A. Hoppe-Seylers Zeit. Physiol. Chem. 1933, 223, 43–52. The -diphenylprolinol obtained in this way, mp 74.0-74.8 °C, [α]D22-68.1° (c 3.17 in CHC13), had 99.0% ee as shown by conversion to the corresponding MTPA amide ((S)-(+)-MTPA acid chloride—methylene chloride aqueous sodium hydroxide at 0 °C, see: Dale, J. A.; Mosher, H. S. J. Am. Chem. Soc. 1973, 95, 512-519.) and HPLC analysis on a DuPont Zorbax silica column using 95:5 hexane-THF for elution, the minor diastereomer being the less polar. The ee values cited above are corrected by adding 1% to the experimentally observed values to correspond to values for optically pure catalyst 3.
7. For previous studies on such monomer—dimer equilibria in related systems, see: Bonnet, J. P. ; Laurent, J. P. J. Inorg. Nucl. Chem. 1970, 12, 1449–1451. Mikhailov B. M.; Bochbareva, M. N.; Bogdanov, V. S.; Boldyreva, O. G.; Dorokhov, V. A. J. Gen. Chem. USSR 1971, 41, 1550–1554. Pretsch, E.; Seibl, J.; Simon, W.; Clerc, T. Spectral Data for Structure Determination of Organic Compounds; Springer-Verlag: Berlin, 1983; p I 260.