Stereoselective synthesis of new 8-oxabicyclo[3.2.1]oct-6-en-2-one and 8-oxabicyclo[3.2.1]octa-3,6-dien-2-one derivatives. The electron-releasing andelectron-withdrawing effects of homoconjugated ketones
P. Gerber et P. Vogel, Stereoselective synthesis of new 8-oxabicyclo[3.2.1]oct-6-en-2-one and 8-oxabicyclo[3.2.1]octa-3,6-dien-2-one derivatives. The electron-releasing andelectron-withdrawing effects of homoconjugated ketones, I J CHEM B, 40(10), 2001, pp. 898-904
Citations number
64
Categorie Soggetti
Organic Chemistry/Polymer Science
Journal title
INDIAN JOURNAL OF CHEMISTRY SECTION B-ORGANIC CHEMISTRY INCLUDING MEDICINAL CHEMISTRY
Two successive brominations of 8-oxabicyclo[3.2.1]oct-6-en-2-one 6 provided
3-exo,6-exo,7-endo-tribromo-7oxabicyclo[3.2.1]octan-2-endo-one 10 with hig
h stereoselectivity. NaBH4 reduced 10 into 3-exo, 6-exo,7-endo-tribromo-8-o
xabicyclo[3.2.1]octan-2-endo-ol exclusively. Selective elimination of one e
quivalent of HBr from 10 furnished 3-exo,7-dibromo-8-oxabicyclo[3.2.1]oct-6
-en-2-endo-ol 13. Regio- and stereoselective addition of PhSeCl to enone 6,
followed by alpha -ketone bromination and treatment with a base led select
ively to 7-(phenylseleno)-8-oxabicyclo[3.2.1]octa-3,6-dien-2-one 20. The hi
gh selectivities observed are attributed to steric factors and to electroni
c factors such as electron-releasing or electron-withdrawing effects of hom
oconjugated carbonyl group.