A process is proposed for preparing unsaturated macrocyclic monoketones, comprising the following steps: (a) providing macrocyclic dienes having a ring size of at least 9 carbon atoms; (b) contacting the starting materials from step (a) with (b1) a palladium(II) salt and/or a palladium(II) complex; and (b2) an oxidizing agent; and (b3) a solvent; and optionally (b4) a ligand; and optionally (b5) a co-catalyst; and optionally (b6) an acid, with the proviso that the co-catalyst (b5) comprises or consists of a divalent or trivalent iron salt which is different from FeSO4 and is preferably iron(III) nitrate.