A process for the preparation of compounds of formula in which R 1a to R 1d, independently of one another, are selected from the group consisting of hydrogen, fluorine, chlorine, bromine, iodine, and also from (C 1 -C 6)-alkyl, where the alkyl radical is unsubstituted or is substituted by one or more substituents selected from the group consisting of fluorine, chlorine, (C 1 -C 4) -alkoxy or (C 3 -C 7)-cycloalkyl, (C 3 -C 8)-cycloalkyl, where the cycloalkyl radical is unsubstituted or is substituted by one or more substituents selected from the group consisting of fluorine, chlorine, (C 1 -C 4)-alkyl or (C 3 -C 7)-cycloalkyl or (C 1 -C 4)-alkoxy, (C 1 -C 6)-alkoxy, where the alkoxy radical is unsubstituted or is substituted by one or more substituents selected from the group consisting of fluorine, chlorine, (C 1 -C 4)-alkoxy or (C 3 -C 7)-cycloalkyl, (C 3 -C 7)-cycloalkoxy, where the cycloalkoxy radical is unsubstituted or is substituted by one or more substituents selected from the group consisting of fluorine, chlorine, (C 1 -C 4)-alkyl or (C 1 -C 4)-alkoxy, (C 1 -C 6)-alkylthio, where the alkylthio radical is unsubstituted or is substituted by one or more substituents selected from the group consisting of fluorine, chlorine, (C 1 -C 4)-alkyl or (C 1 -C 9)-alkoxy, and also from (C 3 -C 7)-cycloalkylthio, where the cycloalkylthio radical is unsubstituted or is substituted by one or more substituents selected from the group consisting of fluorine, chlorine, (C 1 -C 4)-alkyl or (C 1 -C 4)-alkoxy, and also from phenyl or 1-naphthyl or 2-naphthyl or a five- or six-membered heteroaromatic ring having 1 to 2 heteroatoms, where the heteroatoms, independently of one another, are selected from the group consisting of O or N and where the aryl or heteroaryl radical is unsubstituted or is substituted by one or more substituents selected from the group consisting of fluorine, chlorine, bromine, iodine, (C 1 -C 4)-alkyl, (C 1 -C 4) -alkoxy or (C 3 -C 7) -cycloalkyl or (C 1 -C 4)-alkylthio, and R 2 is hydrogen, (C 1 -C 6)-alkyl, where the alkyl radical is unsubstituted or is substituted by one or more substituents selected from the group consisting of fluorine, chlorine, (C 1 -C 4)-alkoxy or (C 3 -C 7)-cycloalkyl, or benzyl, where the benzyl is unsubstituted or is substituted by one or more substituents selected from the group consisting of fluorine, chlorine, bromine, iodine, nitro, (C 1 -C 4) -alkyl, (C 1 -C 4) - alkoxy or (C 3 -C 7)-cycloalkyl or (C 1 -C 4)-alkylthio and also from COOR a, in which R a is a (C 1 -C 4)-alkyl, and -CONR b' R b" or -CONHR b", in which R b' and R b" are each independently of one another a (C 1 -C 4)-alkyl, where in each case two substituents on the N atom together optionally form an unsubstituted or substituted ring, R 3 is hydrogen or methyl, R 4 and R 5, independently of one another, are in each case hydrogen, (C 1 -C 6)-alkyl, where the alkyl radical is unsubstituted or is substituted by one or more substituents selected from the group consisting of fluorine, chlorine, (C 1 -C 4)-alkoxy or (C 3 -C 7)-cycloalkyl, (C 1 -C 6)-alkoxy, where the alkoxy radical is unsubstituted or is substituted by one or more substituents selected from the group consisting of fluorine, chlorine, (C 1 -C 4)-alkoxy or (C 3 -C 7)-cycloalkyl, where an oxindole in which R 1a to R 1d and R 2 and R 3 are as defined in formula, is reacted in a solvent with a triazine in which R 4 and R 5 are as defined in formula, and X, as leaving group, is Cl, Br, I, alkoxy, alkylsulfonyl, (alkylsulfonyl)oxy, haloalkylsulfonyl, phenylsulfonyl or toluene-4-sulfonyl, which comprises carrying out the reaction in the presence of - potassium carbonate or sodium carbonate, - lithium hydroxide, sodium hydroxide, potassium hydroxide, barium hydroxide or tert-alkylammonium hydroxide, - potassium phosphate (K 3 PO 4), potassium hydrogenphosphate (K 2 HPO 4) or sodium phosphate or - in a mixture comprising at least two of the aforementioned bases. - potassium carbonate or sodium carbonate, - lithium hydroxide, sodium hydroxide, potassium hydroxide, barium hydroxide or tert-alkylammonium hydroxide, - potassium phosphate (K 3 PO 4), potassium hydrogenphosphate (K 2 HPO 4) or sodium phosphate or - in a mixture comprising at least two of the aforementioned bases.