The biradicals (IIa, b) formed by γ-hydrogen abstraction on photoexcitation of t-butyl-p-benzoquinones (Ia, b), add to SO2 to give the benzoquinonyl-alkanesulphinic acids (XIIIa, b), which add intramolecularly to form heterocyclic compounds or intermolecularly to quinones and phenolic compounds to form sulphones.
