Stereospecific Anoinically Promoted Transannular Hydride Shifts in Medium-Ring Hydroxy Ketones. Probe of Their Reversibility and the Potential for Regiocontrol
Examples are provided of stereospecific transannular oxidation−reduction processes involving the conjugate bases of δ-hydroxy ketones in a nine-membered ring setting. The ability to control the direction of these equilibria by proper modulation of the solvent environment and level of hydroxyl group protection is demonstrated. MM3-derived steric energies of the isomer pairs suggest that the equilibrium distributions are the outcome of the extent to which intramolecular hydrogen bonding forces are disrupted by polar solvent molecules when present.