Concerning the Boron-mediated aldol reaction of carboxylic esters

Journal of Organic Chemistry

Volumn 61, Issue 8, 1996, Pages 2590-2591

  Abiko, Atsushi ^a   Liu, Ji Feng ^a   Satoru, Masamune ^b  

^a KAO CORPORATION   (Japan)

^b MASSACHUSETTS INSTITUTE OF TECHNOLOGY   (United States)

Author keywords

[No Author keywords available]

Indexed keywords

EID: 0001622595     PISSN: 00223263     EISSN: None     Source Type: Journal    
DOI: 10.1021/jo960252b     Document Type: Article

References (17)

1. For the failure of aldol reactions of carboxylic esters and amides, see: (a) Evans, D. A.; Nelson, J. V.; Vogel. E.; Taber, T. R. J. Am. Chem. Soc. 1981, 103, 3099. (b) Brown, H. C.; Dhar, R. K.; Ganesan, K.; Singaram, B. J. Org. Chem. 1992, 57, 499. (c) Ganesan, K.; Brown, H. C. J. Org. Chem. 1994, 59, 2336. (d) Ganesan, K.; Brown, H. C. J. Org. Chem 1994, 59, 7346.
2. For the failure of aldol reactions of carboxylic esters and amides, see: (a) Evans, D. A.; Nelson, J. V.; Vogel. E.; Taber, T. R. J. Am. Chem. Soc. 1981, 103, 3099. (b) Brown, H. C.; Dhar, R. K.; Ganesan, K.; Singaram, B. J. Org. Chem. 1992, 57, 499. (c) Ganesan, K.; Brown, H. C. J. Org. Chem. 1994, 59, 2336. (d) Ganesan, K.; Brown, H. C. J. Org. Chem 1994, 59, 7346.
3. For the failure of aldol reactions of carboxylic esters and amides, see: (a) Evans, D. A.; Nelson, J. V.; Vogel. E.; Taber, T. R. J. Am. Chem. Soc. 1981, 103, 3099. (b) Brown, H. C.; Dhar, R. K.; Ganesan, K.; Singaram, B. J. Org. Chem. 1992, 57, 499. (c) Ganesan, K.; Brown, H. C. J. Org. Chem. 1994, 59, 2336. (d) Ganesan, K.; Brown, H. C. J. Org. Chem 1994, 59, 7346.
4. For the failure of aldol reactions of carboxylic esters and amides, see: (a) Evans, D. A.; Nelson, J. V.; Vogel. E.; Taber, T. R. J. Am. Chem. Soc. 1981, 103, 3099. (b) Brown, H. C.; Dhar, R. K.; Ganesan, K.; Singaram, B. J. Org. Chem. 1992, 57, 499. (c) Ganesan, K.; Brown, H. C. J. Org. Chem. 1994, 59, 2336. (d) Ganesan, K.; Brown, H. C. J. Org. Chem 1994, 59, 7346.
5. For reviews of boron-mediated aldol reaction, see: (a) Kim, B. M.; Williams, S. F.; Masamune S. Comprehensive Organic Synthesis; Trost, B. M., Fleming, I., Eds.; Pergamon Press: Oxford, 1991; Vol. 2 (Heathcock, C. H., Ed.), Chapter 1.7, p 239.
6. (b) Heathcock, C. H. Modern Synthetic Methods; Scheffold, R., Ed.; VCH: New York, 1992; p 1. Also see ref 1d and references cited therein.
7. (a) Corey, E. J.; Imwinkelried, R.; Pikul, S.; Xiang, Y. B. J. Am. Chem. Soc. 1989, 111, 5493.
8. (b) Corey, E. J.; Kim, S. S. J. Am. Chem. Soc. 1990, 112, 4976.
9. (c) Corey, E. J.; Lee, D.-H. Tetrahedron Lett. 1993, 34, 1737.
10. Brown, H. C ; Ganesan, K. Tetrahedron Lett. 1992, 33, 3421.
11. 2 at -78 °C for 2 h, followed by the addition of isobutyraldehyde at -78 °C for 1 h and then 0 °C 1 h, afforded the aldol product in 50% yield with a ratio of syn:anti = 1:1.
12. 2 group (Scheme 1). Also, the E:Z ratio of an enol borinate is equated to the syn:anti ratio of the aldol products which are derived from the borinate. See ref 1c. Due mainly to the facile E-Z isomerization of the enol borinate, the precise spectral characterization of either isomer (E or Z) has not been completed.
13. Isobutyraldehyde (instead of benzaldehyde) was used in order to avoid the Lewis acid-catalyzed aldol reaction, which is sometimes the main reaction pathway. See: Danda, H.; Hansen, M. N.; Heathcock, C. H. J. Org. Chem. 1990, 55, 173.
14. Corey, E. J.; Peterson, R. T. Tetrahedron Lett. 1985, 26, 5025.
15. Dicyclohexylboron triflate formed a complex with the amine in competition with deprotonation, and there existed no free cyclohexylboron triflate after 3 h at -78 °C in the experiments using either 1.3 or 2.0 equiv of the inflate.
16. Isomerization of enol borinates under rather forcing conditions. (a) Masamune, S.; Mori, S.; van Horn, D.; Brooks, D. W. Tetrahedron Lett. 1979, 1665. (b) Reference 1a.
17. Isomerization of enol borinates under rather forcing conditions. (a) Masamune, S.; Mori, S.; van Horn, D.; Brooks, D. W. Tetrahedron Lett. 1979, 1665. (b) Reference 1a.