5- and 6-Exo Radical Cyclizations of γ-Oxygenated-α,β-Unsaturated Sulfones

Synlett

Volumn 1996, Issue 7, 1996, Pages 640-642

  Adrio, Javier ^a   Carretero, Juan C ^a   Arrayás, Ramón Gómez ^a  

^a UNIVERSIDAD AUTÓNOMA DE MADRID   (Spain)

Author keywords

[No Author keywords available]

Indexed keywords

EID: 0001960418     PISSN: 09365214     EISSN: None     Source Type: Journal    
DOI: 10.1055/s-1996-5543     Document Type: Article

References (20)

1. a) Motherwell, W. B.; Crich, D. "Free-radical Reactions in Organic Synthesis" Academic Press, London, 1992.
2. For a recent review, see: b) Giese, B.; Kopping, B.; Göbel, T.; Dickhaut, J.; Thoma, G.; Kulicke, K.J.; Trach, F. Organic Reactions 1996, 8, 301-856.
3. For a recent review, see: Bunce, R. A. Tetrahedron 1995, 51, 13103.
4. Simpkins, N. S. "Sulphones in Organic Synthesis" Pergamon Press, Oxford, 1993.
5. a) Carretero, J. C. Gómez Arrayás,; R. J. Org. Chem. 1995, 60, 6000;
6. b) Domínguez, E.; Carretero, J. C. Tetrahedron 1994, 50, 7557.
7. c) De Bias, J.; Carretero J. C.; Domínguez, E. Tetrahedron Lett. 1994, 35, 4603.
8. Domínguez, E.; Carretero, J. C. Tetrahedron 1990, 57, 3867.
9. 2 at rt .
10. 2 at rt.
11. 3SnH (0.26 ml, 1.1 mmol) and AIBN (16.4 mg, 0.10 mmol) in one portion. The resulting mixture was heated at reflux for 3h and volatiles were removed under reduced pressure. The residue was purified by flash cromatography (first the organotin by-products were eluted with hexane followed by elution with mixtures of hexane: AcOEt).
12. This low stereoselectivity agrees with that previously described for a similar substrate: Ogura, K.; Kayano, A.; Fujino, T.; Sumitani, N.; Fujita, M. Tetrahedron Lett. 1993, 34, 8313.
13. 1 in axial position).
14. a) Beckwith, A. L. J.; Easton, C. J.; Serelis, A. K. J. Chem. Soc., Chem. Commun. 1980, 482 and 484.
15. b) Beckwith, A. L. J. Tetrahedron 1981, 37, 3073. See also: Spellmeyer, D. C.; Houk, K. N. J. Org. Chem. 1987, 52, 959.
16. b) Beckwith, A. L. J. Tetrahedron 1981, 37, 3073. See also: Spellmeyer, D. C.; Houk, K. N. J. Org. Chem. 1987, 52, 959.
17. β,γ (< 3.7 Hz for all substrates 1 and 2). This conformational effect would favour the transition state A (conformationally similar to E) to a larger extent than B (conformationally similar to F) in the radical cyclizations. For conformational preferences of allylic alcohols and derivatives, see: a) Gung, B. W.; Wolf, M. A. J. Org. Chem. 1993, 55, 7038. b) Gung, B. W.; Melnick, J. P.; Wolf, M. A.; King, A. J. Org. Chem. 1995, 60, 1947. (Equation Presented)
18. β,γ (< 3.7 Hz for all substrates 1 and 2). This conformational effect would favour the transition state A (conformationally similar to E) to a larger extent than B (conformationally similar to F) in the radical cyclizations. For conformational preferences of allylic alcohols and derivatives, see: a) Gung, B. W.; Wolf, M. A. J. Org. Chem. 1993, 55, 7038. b) Gung, B. W.; Melnick, J. P.; Wolf, M. A.; King, A. J. Org. Chem. 1995, 60, 1947. (Equation Presented)
19. Lee, E.; Tae, J. S.; Lee, C.; Park, C. M. Tetrahedron Lett. 1993, 34, 4831.
20. The stereochemistry of cis-8, cis-10 and trans-10 has been firmly established by NMR. In the figures shown below are summarized the NOE's and coupling constants that were particularly diagnostic for the configurational assignment.