On the stereochemistry of the dihydropyrone Diels-Alder reaction

Organic Letters

Volumn 1, Issue 9, 1999, Pages 1411-1414

  Seth, Punit P ^a   Totah, Nancy I ^a  

^a E11 SSH   (United States)

Author keywords

[No Author keywords available]

Indexed keywords

EID: 0003468214     PISSN: 15237060     EISSN: None     Source Type: Journal    
DOI: 10.1021/ol9909637     Document Type: Article

References (20)

1. (a) Chen, D.; Wang, J.; Totah, N. I. J. Org. Chem. 1999, 64, 1776.
2. (b) Seth, P. P.; Totah, N. I. J. Org. Chem., in press.
3. (a) Cremins, P. J.; Saengchantara, S. T.; Wallace, T. W. Tetrahedron 1987, 43, 3075.
4. (b) Hsung, R. P. J. Org. Chem. 1997, 62, 7904.
5. (a) Liu, H. J.; Ngooi, T. K.; Browne, E. N. C. Can. J. Chem. 1988, 66, 3143.
6. (b) Liu, H. J.; Chew, S. Y.; Browne, E. N. C. Tetrahedron Lett. 1991, 56, 2005.
7. (c) Fringuelli, F.; Taticchi, A.; Wenkert, E. Org. Prep. Proced. Int. 1990, 22, 131.
8. 3c Thus, the methoxy substituent at C5 and the W substituent at C4a will be trans in the endo cycloadduct.
9. (a) Kozmin, S. A.; Rawal, V. H. J. Org. Chem. 1997, 62, 5252.
10. (b) Kozmin, S. A.; Janey, J. M.; Rawal, V. H. J. Org. Chem. 1999, 64, 3039.
11. 1b Optimized conditions are used in the present studies.
12. Upon purification, a single diastereomer was isolated.
13. That the ratios obtained in the above experiments reflect a kinetic process is supported by a lack of equilibration when individual isomers of 10a and 12a are resubjected to either thermal or Lewis acid catalyzed reaction conditions.
14. 4.
15. Ginsburg, D. Tetrahedron 1983, 39, 2095.
16. The use of Lewis acid to catalyze the Diels-Alder reactions of electron-deficient olefin dienophiles with electron-rich dienes remains largely unexplored, presumably due to the considerable reactivity of these dienes under thermal conditions as well as their lability to many Lewis acids.
17. Rubottom, G. M. Vazquez, M. A.; Pelegrina, D. R. Tetrahedron Lett. 1974, 4319.
18. That compounds 16 and 16a are ketone and hemiketal forms of the same isomer is supported by the formation of a 1:1 mixture of diastereomers (16:17) when the oxidation is run in hexanes. Compound 17 can be cleanly separated from the mixture of 16 and 16a. (Matrix presented)
19. Use of the TBDMS derivative of Danishefsky's diene facilitates isolation of the cycloadducts. Selectivities are comparable to those reported previously using the parent diene (TMS ether). An exception is noted in ref 15.
20. The thermal Diels-Alder reactions of both tert-butyl and benzyl ester derivatives 18 with Danishefsky's diene are reported to occur with complete endo diastereoselectivity, though the cycloadducts are recovered in only 52% and 53% yields, respectively: Groundwater, P. W.; Hibbs, D. E.; Hursthouse, M. B. J. Chem. Soc., Perkin Trans. 1 1997, 163.