Sequenced reactions involving squarate esters. The first suggestion that helical equilibration within the advanced octatetraene intermediate is responsible for stereochemical control

Tetrahedron Letters

Volumn 37, Issue 19, 1996, Pages 3299-3302

  Paquette, Leo A ^a   Doyon, Julien ^a   Kuo, Lung Huang ^a  

^a OHIO STATE UNIVERSITY   (United States)

Author keywords

[No Author keywords available]

Indexed keywords

CYCLOPENTANE DERIVATIVE; POLYCYCLIC HYDROCARBON;

ARTICLE; CHIRALITY; DRUG SYNTHESIS; REACTION ANALYSIS; STEREOCHEMISTRY; TECHNIQUE;

EID: 0030011950     PISSN: 00404039     EISSN: None     Source Type: Journal    
DOI: 10.1016/0040-4039(96)00580-1     Document Type: Article

References (12)

1. Negri, J. T.; Morwick, T.; Doyon, J.; Wilson, P. D.; Hickey, E. R.; Paquette, L. A. J. Am. Chem. Soc. 1993, 115, 12189.
2. (a) Morwick, T.; Doyon, J.; Paquette, L. A. Tetrahedron Lett. 1995, 36, 2369.
3. (b) Paquette, L. A.; Morwick, T. J. Am. Chem. Soc. 1995, 117, 1451.
4. (c) Paquette, L. A.; Doyon, J. J. Am. Chem. Soc. 1995, 117, 6799.
5. (d) Wilson, P. D.; Friedrich, D.; Paquette, L. A. J. Chem. Soc., Chem. Commun. 1995, 1351.
6. (a) Rondan, N. G.; Houk, K. N. J. Am. Chem. Soc. 1985, 107, 2099.
7. (b) Thomas, B. E., IV; Evanseck, J. D.; Houk, K. N. J. Am. Chem. Soc. 1993, 115, 4165.
8. To prove equilibration requires either high yields of a single product or preferably independent demonstration that the sterically more crowded helix, when purposely formed, also gives rise to the same product rather than uncharacterizable materials. Due to the many individual steps associated with the cascade, overall reaction efficiencies usually peak at the 50-70% level. However, it has recently proven possible to separate a pair of diastereomeric monoadducts and to demonstrate that these compounds lead to the identical polycyclic product when subjected to further reaction (Kuo, L. H., unpublished results).
9. Prepared by treating the bromide [Paquette, L. A.; Dahnke, K.; Doyon, J.; He, W.; Wyant, K.; Friedrich, D. J. Org. Chem. 1991, 56, 6199] with 2 equiv of tert-butyllithium in THF at -78°C.
10. 3N; DBU), saponification, and brominative decarboxylation according to reference 5.
11. 3 display other distinguishing features as well. For example, while the methyl substituent in 14 appears as a doublet (J = 7 Hz) at δ 1.17, that in 15 is seen as a singlet at δ 1.12.
12. We thank the National Science Foundation for support of this research.