Process for the preparation of linear quinacridones

Process for the preparation of linear quinacridones of the formula (1) (1) in which R denotes a hydrogen, fluorine, chlorine or bromine atom or a C1-C6-alkyl, C1-C3-alkoxy or phenyl group or a fused benzene ring or a phenylamino or phenoxy group which can be substituted on the aromatic nucleus by fluorine, chlorine or bromine atoms or C1-C4-alkyl groups, and n denotes a number from 0 to 2, it being possible, in the event that n NOTEQUAL 0, for the substituents R present on the same benzene ring or on the two benzene rings to be identical or different, by the oxidation of linear 6,13-dihydroquinacridones of the formula (2) (2) in which R and n have the meanings mentioned above, which comprises heating, at temperatures from about 180 DEG C. to about 280 DEG C., 1 mole of the last-mentioned compounds with 1 to 2 moles of iodine in a high-boiling organic solvent which is inert towards the reactants.