Process for preparing compounds of the formula in which Ar is the where R 1, R 2, R 3, R 4 and R 5 are the same or different and are each independently hydrogen, amino, cyano, nitro, halogen, optionally halogen-substituted C 1 -C 6 -alkyl, C 1 -C 6 -thioalkyl, thiophenyl, C 1 -C 6 -alkoxy, C 6 -C 10 -aryloxy, phenyl, -CO-C 6 -C 10 -aryl, -CO-C 1 -C 3 -alkyl, -COO-C 1 -C 6 -alkyl or -COO-C 6 -C 10 -aryl, the Ar radical may additionally also be a heteroaromatic radical or the Ar radical may also be 1- or 2-naphthyl, and R 6 and R 7 are each independently optionally substituted C 1 -C 8 -alkyl, phenyl, aryl, or NR 8 R 9, where R 8 and R 9 are the same or different and are each independently C 1 -C 4 -alkyl, or phenyl optionally substituted by optionally fluorine- or chlorine-substituted C 1 -C 3 -alkyl, by nitro, cyano or di-C 1 -C 3 -alkylamino, or together with the nitrogen atom to which they are bonded are a saturated or unsaturated, substituted or unsubstituted cycle, characterized in that aryl or heteroaryl halides of the formula Ar-Hal in which Hal is chlorine, bromine or iodine and Ar is as defined above, are reacted with malonic esters of the formula in which R 6 and R 7 are each as defined above in the presence of a palladium catalyst, of a phosphine ligand and A) of an inorganic base and of a phase transfer catalyst optionally using an organic solvent. R 1, R 2, R 3, R 4 and R 5 are the same or different and are each independently hydrogen, amino, cyano, nitro, halogen, optionally halogen-substituted C 1 -C 6 -alkyl, C 1 -C 6 -thioalkyl, thiophenyl, C 1 -C 6 -alkoxy, C 6 -C 10 -aryloxy, phenyl, -CO-C 6 -C 10 -aryl, -CO-C 1 -C 3 -alkyl, -COO-C 1 -C 6 -alkyl or -COO-C 6 -C 10 -aryl, the Ar radical may additionally also be a heteroaromatic radical or the Ar radical may also be 1- or 2-naphthyl, and R 6 and R 7 are each independently optionally substituted C 1 -C 8 -alkyl, phenyl, aryl, or NR 8 R 9, where R 8 and R 9 are the same or different and are each independently C 1 -C 4 -alkyl, or phenyl optionally substituted by optionally fluorine- or chlorine-substituted C 1 -C 3 -alkyl, by nitro, cyano or di-C 1 -C 3 -alkylamino, or together with the nitrogen atom to which they are bonded are a saturated or unsaturated, substituted or unsubstituted cycle, characterized in that aryl or heteroaryl halides of the formula Ar-Hal in which Hal is chlorine, bromine or iodine and Ar is as defined above, are reacted with malonic esters of the formula in which R 6 and R 7 are each as defined above in the presence of a palladium catalyst, of a phosphine ligand and A) of an inorganic base and of a phase transfer catalyst optionally using an organic solvent. Hal is chlorine, bromine or iodine and Ar is as defined above, are reacted with malonic esters of the formula in which R 6 and R 7 are each as defined above in the presence of a palladium catalyst, of a phosphine ligand and A) of an inorganic base and of a phase transfer catalyst optionally using an organic solvent. R 6 and R 7 are each as defined above in the presence of a palladium catalyst, of a phosphine ligand and A) of an inorganic base and of a phase transfer catalyst optionally using an organic solvent. A) of an inorganic base and of a phase transfer catalyst optionally using an organic solvent.