Unusual diastereoselectivity in intramolecular Diels-Alder reactions of substituted 3,5-hexadienyl acrylates. Preference for a boatlike structure of the six-atom tether due to ester overlap

Organic Letters

Volumn 2, Issue 13, 2000, Pages 1835-1837

  Jung, Michael E ^a   Huang, Adrian ^a   Johnson, Ted W ^a  

^a UNIVERSITY OF CALIFORNIA   (United States)

Author keywords

[No Author keywords available]

Indexed keywords

EID: 0000719534     PISSN: 15237060     EISSN: None     Source Type: Journal    
DOI: 10.1021/ol000104e     Document Type: Article

References (15)

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2. Martin, S. F.; Williamson, S. A.; Gist, R. P.; Smith, K. M. J. Org. Chem. 1983, 48, 5170.
3. Mitsunobu, O. Synthesis 1981, 1.
4. Buss, A. D.; Hirst, G. C.; Parson, P. J. J. Chem. Soc., Chem. Commun. 1987, 1836.
5. (b) For the preparation of the corresponding ester, which can be reduced to the alcohol using lithium aluminum hydride, see: Shing, K. M.; Tang, Y. Tetrahedron 1990, 46, 2187.
6. Pirrung, M. C.; Han, H.; Ludwig, R. T. J. Org. Chem. 1994, 59, 2430.
7. a with the carbonyl group in 8b. This proton appears at quite low field (δ 2.8-3.4, depending on solvent) as a doublet of septets due to this interaction, which is possible only in this half chair-chair trans conformation. For a similar argument in the xestobergsterol class of antihistamines, see: Jung, M. E.; Johnson, T. W. J. Am. Chem. Soc. 1997, 119, 12412.
8. For a discussion of these conformational and/or stereochemical issues and for the references to the energies quoted, see: Eliel, E. L.; Wilen, S. H. Stereochemistry of Organic Compounds; Wiley-Interscience: New York, 1994; pp 619, 689, and 1193.
9. See for example: (a) Coe, J. W.; Roush, W. R. J. Org. Chem. 1989, 54, 915.
10. (b) Roush, W. R. In Comprehensive Organic Synthesis; Trost, B. M., Ed.; Pergamon: Oxford, 1991; Vol. 5. Chapter 4.4, pp 513-550.
11. 6 (10) Kolb, H. C.; Van Nieuwenhze, M. S.; Sharpless, K. B. Chem. Rev. 1994, 94, 2483.
12. There is a very small amount of another minor isomer (accounting for about 20% of the minor product 13b) which was not isolated in pure form but most likely is the other cis ring juncture compound, C, e.g., that produced from the endo chairlike transition state A.
13. Alexakis, A.; Jachiet, D.; Toupet, L. Tetrahedron 1989, 45, 6203.
14. Mori reported that the analogue having an acetyl group on the distal carbon of the enoate i afforded the trans-fused product ii as the only crystalline product isolated in 54% yield. However, it is well-known that activating groups at the distal end of alkenes often dominate the stereocontrol of intramolecular Diels-Alder reactions and therefore these systems are not directly comparable. Mori, K.; Gupta, A. K. Tetrahedron 1985, 41, 5295. The structural assignment of ii indicates that an equilibration of one of the two carbonyl functions must have occurred since the stereochemistry of the alkene is not retained in the Diels-Alder reaction, i.e., either the proton α to the acetyl group or α to the lactone carbonyl has been epimerized in the product. (formula presented)
15. After the original submission of this manuscript, we learned of a very similar study by Kurth, et al., who recently presented a poster on this work. Kurth, M. J.; Kim, P.; Olmstead, M. M.; Nantz, M. H. 219th Natiional Meeting of the American Chemical Society, San Francisco, March 26-30, 2000; ORGN 343.