Alkene substituents for selective activation of endo-regioselective polyepoxide oxacyclizations

Organic Letters

Volumn 6, Issue 24, 2004, Pages 4487-4489

  Bravo, Fernando ^a,b   McDonald, Frank E ^a   Neiwert, Wade A ^a   Hardcastle, Kenneth I ^a  

^a EMORY UNIVERSITY   (United States)

^b GSK   (Italy)

Author keywords

[No Author keywords available]

Indexed keywords

ALKENE DERIVATIVE; BROMOOXEPANE; CARBENE; EPOXIDE; ETHER DERIVATIVE; FUNCTIONAL GROUP; OXEPANE DERIVATIVE; POLYCYCLIC HYDROCARBON; UNCLASSIFIED DRUG;

ALKYNYLATION; ARTICLE; CYCLIZATION; POLYMERIZATION; QUANTUM YIELD; REACTION ANALYSIS; SEPARATION TECHNIQUE; STEREOCHEMISTRY; TRANS ISOMER;

ALKENES; CYCLIZATION; EPOXY COMPOUNDS; POLYCYCLIC COMPOUNDS;

EID: 10044244964     PISSN: 15237060     EISSN: None     Source Type: Journal    
DOI: 10.1021/ol048212e     Document Type: Article

References (27)

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3. Bravo, F.; McDonald, F. E.; Neiwert, W. A.; Do, B.; Hardcastle, K. I. Org. Lett. 2003, 5, 2123.
4. Boc-protected pentaepoxide alcohol 4 was synthesized from the corresponding pentaene alcohol in a sequence of reactions similar to the ones described for geraniol, farnesol, and geranylgeraniol derivatives in ref 1. The pentaene alcohol, in turn, was prepared by coupling of the organobarium reagent derived from farnesyl chloride (see ref 4) with 8-bromo-1-O-tert- butyldiphenylsilyl-3,7-dimethyl-octa-2,6-dien-1-ol (ref 5). See Supporting Information for details.
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19. ( 11 ) Use of n-butyllithium or phenyllithium in the Wittig reaction leading to 16 considerably reduced the yield of the methylenation to 20-25%.
20. See Supporting Information for essential data and thermal ellipsoid diagrams for crystal structures obtained for compounds ent-17 and 19.
21. Cyclization of diepoxide 1 (Scheme 1) under the optimized conditions (ytterbium(III) triflate) gave the bicyclic product 5 in 52% yield, demonstrating that the vinyl substituent in substrate 15 plays a significant role in enhancing the cyclization yield.
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24. The only related synthesis of halooxepanes from hydroxyalkene synthesis requires alkoxy-substituted alkenes in order to achieve endoregioselectivity: (a) Brunel, Y.; Rousseau, G. J. Org. Chem. 1996, 61, 5793. (b) Simart, F.; Brunel, Y.; Robin, S.; Rousseau, G. Tetrahedron 1998, 54, 13557.
25. 2O were not suitable solvents for this transformation.
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