Enantio- and diastereoselective synthesis of anti-α-bromo-α-fluoro-β-hydroxycarboxylates

Synlett

Volumn , Issue 4, 1998, Pages 437-439

  Iseki, Katsuhiko ^a   Kuroki, Yoshichika ^a   Kobayashi, Yoshiro ^a  

^a DAIKIN INDUSTRIES LTD   (Japan)

Author keywords

[No Author keywords available]

Indexed keywords

EID: 0002526632     PISSN: 09365214     EISSN: None     Source Type: Journal    
DOI: 10.1055/s-1998-1677     Document Type: Article

References (18)

1. For reviews see: (a) Welch, J. T. Tetrahedron 1987, 43, 3123.
2. (b) Bravo, P.; Resnati, G. Tetrahedron: Asymm. 1990, 1, 661.
3. (c) Resnati, G. Tetrahedron 1993, 49, 9385.
4. (a) Biomedical Aspects of Fluorine Chemistry; Filler, R.; Kobayashi, Y. Eds.; Kodansha Ltd. and Elsevier Biomedical Press: Tokyo and Amsterdam, 1982.
5. (b) Biomedical Frontiers of Fluorine Chemistry; Ojima, I.; McCarthy, J. R.; Welch, J. T. Eds.; American Chemical Society: Washington, D. C., 1996.
6. Iseki, K.; Kuroki, Y.; Kobayashi, Y. Tetrahedron Lett. 1997, 38, 7209.
7. 3; 133.1 (s, 0.62F), 134.5 (s, 0.38F)]. The minor isomer was confirmed to be the (Z)-acetal by the NOE between F and the methylene proton of the ethoxy group. (Chemical Equation Presented)
8. 2 at 45°C for 1 h. See: (a) Parmee, E. R.; Tempkin, O.; Masamune, S. J. Am. Chem. Soc. 1991, 113, 9365.
9. (b) Parmee, E. R.; Hong, Y.; Tempkin, O.; Masamune, S. Tetrahedron Lett. 1992, 33, 1729.
10. Elevating the reaction temperature to -20°C and stirring for 2 h after 1 h at -78°C did not affect the anti/syn ratio (53/47): anti-3a [99% ee (+)]; syn-3a [99% ee (+)].
11. The enantioselectivities of the anti-aldols obtained at -78°C are as follows: 3b: 98% ee (+); 3c: 98% ee (+); 3d: 89% ee (+); 3e: 98% ee (+); 3f: 97% ee (+); 3g: 90% ee (2R,3R). See ref. 3.
12. In the case of the dimethylketene methyl trimethylsilyl acetal, elevating the reaction temperature to -20°C does not cause reversal of the enantiofacial selection although the degree of enantioselectivity decreases.
13. Kuwajima, I.; Kato, M.; Mori, A. Tetrahedron Lett. 1980, 27, 4291.
14. 2 at -78°C showed almost the same spectrum as that at -20°C.
15. Mikami et al. proposed the silatropic ene mechanism for the asymmetric catalysis of aldol-type reactions with ketene silyl acetals. See: (a) Mikami, K.; Matsukawa, S. J. Am. Chem. Soc. 1994, 116, 4077.
16. (b) Mikami, K.; Matsukawa, S.; Sawa, E.; Harada, A.; Koga, N. Tetrahedron Lett. 1997, 38, 1951.
17. The aldol reaction catalyzed by a bidentate Lewis acid was reported by Maruoka et al. See: Ooi, T.; Takahashi, M.; Maruoka, K. J. Am. Chem. Soc. 1996, 118, 11307.
18. Iseki, K.; Kuroki, Y.; Asada, D.; Takahashi, M.; Kishimoto, S.; Kobayashi, Y. Tetrahedron 1997, 53, 10271.