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 is capable of dimerization or can be introduced into a high-yielding photoprotolytic oxametathetic sequence. This allows for an expeditious growth of molecular complexity over a few experimentally simple steps with stereochemistry being defined and locked at the very first Diels–Alder step. The overall reaction can potentially be utilized in diversity-oriented synthesis as it allows for three or more diversity inputs furnishing novel unique polycyclic scaffolds, which can readily be decorated with a variety of functionalities and aromatic/heterocyclic pendants.