Diazotization of 4-[N-(4,6-dimethyl-2-pyrimidinyl)sulfamoyl]aniline (I) by means of sodium nitrite in diluted hydrochloric acid gives a corresponding diazonium salt (II), which is then reacted with salicylic acid (III) to afford the 2-hydroxy intermediate (IV). Disalazine is obtained by the reaction of (IV) with acetic anhydride or acetyl chloride.