Importance of Oxyanion Orientation to the Stereochemical Control of Anionic Oxy‐Cope Rearrangements

The enantiomerically pure alcohols 1 and 2 react in an anionic oxy-Cope rearrangement to afford mixtures of (S)- and (R)-4-methyl-5-hexenal(3 and ent-3, respectively). The findings demonstrate that transition states with the oxido group in equatorial position are not as favored in acyclic systems as previously assumed. The oxido group occupies an axial position in 36–40% of the transition states.