Chromium(VI) Oxide-Catalyzed Benzylic Oxidation with Periodic Acid

CrO3 has been found to be an efficient catalyst for benzylic oxidation with periodic acid as the terminal oxidant in acetonitrile. Substituted toluenes with an electron-withdrawing group at the 4- or 3-position and diarylmethanes such as diphenylmethane and fluorene were oxidized to the corresponding substituted benzoic acids and ketones in excellent yields. Benzyl ethers such as isochroman and phthalan were converted to 3,4-dihydroisocoumarin and phthalide in quantitative yields.