First example of intramolecular [2π + 2π] alkene-arene photocyclization in the chromone series and its synthetic utility

Diels-Alder adducts of chromones are shown to undergo an intramolecular [2π + 2π] alkene-arene photocyclization, leading to a versatile polycyclic diene which can dimerize or can be introduced into photoprotolytic oxametathesis.