Process for the preparation of triazinyl-substituted oxindoles of formula (3) and salts thereof by reacting an oxindole (1) with a triazine (2) in the presence of a carbonate, a hydroxide, a phosphate or a mixture of two or more of the aforementioned compounds, and also the compounds of formula (3) and salts thereof (3″) and the use of both for producing crop protection agents.