Stereospecific anionically 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 pr ocesses involving the conjugate bases of delta -hydroxy ketones in a nine-m embered ring setting. The ability to control the direction of these equilib ria by proper modulation of the solvent environment and level of hydroxyl g roup protection is demonstrated. MM3-derived steric energies of the isomer pairs suggest that the equilibrium distributions are the outcome of the ext ent to which intramolecular hydrogen bonding forces are disrupted by polar solvent molecules when present.