The cocatalytic effect of SnO2 on the iron(III) porphyrins-catalyzed aerobic Baeyer-Villiger oxidation of cyclohexanone in the presence of benzaldehyde as reductant was investigated, the conversion of cyclohexanone was remarkablely enhanced, reaching up to 96%. The major role of SnO2 was to active cyclohexanone molecules, which was confirmed by in situ Raman spectroscopy. A plausible cocatalytic mechanism involving the activated cyclohexanone was proposed. (C) 2013 Elsevier B.V. All rights reserved.