SYNTHESIS OF 4- AND 5-SUBSTITUTED 10-OXATRICYCLO2,16>DECADIENONES. FUNCTIONALIZATION OF THE CYCLO-ADDUCT OF FURAN AND CYCLOPENTEN-1,4-DIONE.

Article abstract of DOI:10.1016/S0040-4020(01)89179-1

Tosylmethylation of the furan derived cyclo-adduct of cyclopentene-1,4-dione, followed by O-ethylation, leads to 5-ethoxy-4-(p-tolylsulphonyl)methyl-exo-10-oxatricyclo<5.2.1.0^2.6>dien-3-one 14.This sulpone undergoes a smooth displacement of the tosyl group by an ether or thioether function when treated with alcoholates or thiolates.This displacement involves two sonsecutive S_N2' substitutions, taking place stereospecifically at the least hindered exo-face of the substrate molecule, i. e. anti to the oxa-bridge.Subsequent reduction with DIBAL or reaction with MeLi provides 4- and/or 5-substituted 10-oxatricyclo<5.2.1.0^2.6>decadienones.