Several manganese(III) porphyrin complexes were evaluated as catalysts in the oxidation of indane and tetralin with hydrogen peroxide, in the presence of ammonium acetate as a co-catalyst. Catalysis by Mn(Ill) meso-tetra-2,6-dichlorophenylporphyrins gave rise, in a first stage, to benzylic monooxygenation products (1-alcohols and 1-ketones). However, addition of excess of oxidant gave rise to overoxidation products and, in certain conditions, hydroxy-keto compounds were selectively obtained. Reactions catalysed by Mn(Ill) mesotetra-pentafluorophenylporphyrins showed higher capability to generate dehydrogenated products. As a result, 1H-indene and naphthalene were formed. To understand the reactions' pathway, the oxidations of 1-indanol, 1-indanone, 2-indanol, 1H-indene, 1-tetralol, 1-tetralone, 1,4-dihydroxytetralin and 4-hydroxy-1-tetralone were also considered with manganese (111) meso-tetra-2,6-dichlorophenylporphyiin chloride, Mn(TDCPP)Cl, as catalyst. (c) 2005 Elsevier B.V. All rights reserved.