Strained to the limit: when a cyclobutyl moiety becomes a thermodynamic sink in a protolytic ring-opening of photogenerated oxetanes.

Strained polycyclic oxetanes generated photochemically from the Diels-Alder adducts of cyclic dienes and enones undergo deep skeletal rearrangements under protolytic ring-opening conditions offering expeditious access to chlorohydrins and other products of unique skeletal topology.