SPIRO-FUSED 2,5-CYCLOHEXADIENONES FROM THERMAL 1,3-SHIFTS IN QUINOL VINYL ETHERS - REACTIONS IN NONBENZENOID SYSTEMS AND LIMITATIONS OF THE CHEMISTRY

Addition of functionalized organolithium compounds to quinone monoketals furnished 4-hydroxy-2,5-cyclo-hexadienone derivatives. The 4-hydroxyl group of these molecules was then transformed into a vinyl ether, and the thermal [1,3]-shift chemistry of these functionalized vinyl ethers was studied. In dienone derivatives wherein a [3,3]-sigmatropic shift was not stereoelectronically possible, these molecules underwent thermal and photochemical [1,3]-oxygen-to-carbon migration, affording spiro-2,5-cyclohexadienones in good yield. However, for compounds in which the [3,3]-shift involving the vinyl ether was possible, this reaction occurred at or below room temperature. 1,5-Cyclooctadienebis(methyldiphenylphosphine)iridium hexafluorophosphate was found to be an especially efficient catalyst for the allyl-to-vinyl ether isomerization in these systems.