Aromatic Cations from Oxidative Carbon–Hydrogen Bond Cleavage in Bimolecular Carbon–Carbon Bond Forming Reactions

Chromenes and isochromenes react quickly with 2,3-dichloro-5,6-dicyano-1,4-benzoquinone
(DDQ) to form persistent aromatic oxocarbenium ions through oxidative
carbon–hydrogen cleavage. This process is tolerant of electron-donating
and electron-withdrawing groups on the benzene ring and additional
substitution on the pyran ring. A variety of nucleophiles can be added
to these cations to generate a diverse set of structures.