Oxidation of 1-arylprop-1-enes by using the reagent system CrO₃-HClO₄-CH₃CN at 0-5°C gave seven products from methyl isoeugenol, five from ethyl isoeugenol, four from benzyl isoeugenol, and five from isosafrole. Cagayanone was obtained from isosafrole in one step. The structures of the products were elucidated and the mechanism of their formation is discussed.