[1] The modification is immensely appealing as a result of the two new disparately placed functional groups that lend themselves well to a variety of previously unavailable synthetic manipulations.
Both the neutral and anionic variants of the oxy-Cope rearrangement may occur via either concerted or stepwise radical pathways, although the former mode is generally favored.
[11] The concerted, synchronous pathways presented above generally predominate; it was calculated for anionic oxy-Cope processes that a divide of 17-34 kcal/mol favors heterolysis over homolysis.
[9] The large degree of strain and the presence of a methyl group's bulk favored the (Z)- instead of the expected (E)-cyclooctenone isomer, suggesting that the intermediate is not formed synchronously.
[9] A study on the anionic oxy-Cope rearrangement carried out entirely in the gaseous phase reported that the rate enhancement stems not from solvent interactions, but from those within the structure itself.
[15] Finally, the relief of ring strain over the course of a rearrangement will drive a reaction more forcibly to completion, thereby increasing its rate.
Because there exist multiple classes of natural products containing eight-membered rings, the syntheses of which having proved difficult, the anionic oxy-Cope rearrangement has been highlighted as a suitable alternative pathway.
This goal was achieved in the synthesis of the cis-hydroazulenone below, in which the oxy-Cope intermediate was characterized by a stereoelectronic configuration amenable to remote SN displacement.
[18] Potassium hydride, a frequently utilized reagent for the anionic oxy-Cope rearrangement, is occasionally contaminated with trace impurities that have been suggested to destroy the dienolate intermediate, resulting in putative polymerization.
Macdonald et al., who documented the occurrence, prescribed pre-treatment with iodine to eliminate any potassium superoxide that may persist within a purchased batch of the material.