Abstract4,4‐Dimethoxy‐2,5‐cyclohexadienones9–14were prepared from the corresponding hydroquinone monomethyl ethers by oxidation with thallium trinitrate in methanol. Irradiation of solutions of9–13in methanol with a broad band of UV light centered at 350 nm in a Rayonet reactor afforded 2‐cyclopentenone derivatives15–19in moderate to excellent yields, whereas irradiation of14in methanol gave phenol 8 along with other unidentified products. Irradiation of11–14in benzene yielded substituted phenols. The plausible reaction pathways for the product formatio