Abstract: The invention relates to the use of compounds of the formula IR.sup.1.sub.a Re.sub.b O.sub.c (I),where a is from 1 to 6, b is from 1 to 4 and c is from 1 to 14 and the sum of a, b and c is in accordance with the valence of from 5 to 7 of the rhenium, with the proviso that c is not greater than 3.multidot.b, and where R.sup.1 is identical or different and is an aliphatic hydrocarbon radical having from 1 to 10 carbon atoms, an aromatic hydrocarbon radical having from 6 to 10 carbon atoms or an arylalkyl radical having from 7 to 9 carbon atoms, with the radicals R.sup.1 being able, if desired, to be identically or differently substituted independently of one another and, in the case of .sigma.-bonded radicals, at least one hydrogen atom still being bonded to the carbon atom in the .alpha. position, as catalysts for the oxidation of electron-rich aromatic compounds and their derivatives and to a process for the oxidation of electron-rich aromatic compounds which comprises oxidizing electron-rich C.sub.6 -C.sub.