To an agitated solution of 3.7 g of 5-amino-2-chloro-N-[(4-methoxy-6-methyl-1,3,5-triazin-2-yl)aminocarbonyl]benzenesulfonamide and 0.88 g of sodium cyanoborohydride in 50 ml of acetonitrile is added 3 ml of formalin. To the reaction mixture is then added 1 ml of glacial acetic acid over a period of 10 minutes. The reaction is then stirred at room temperature for 2 hours, another ml of glacial acetic acid is added and stirring is continued for an additional 30 minutes. The reaction mixture is then poured into 50 ml of water, brought to pH 7 by the addition of aqueous sodium hydroxide and extracted several times with methylene chloride. The combined methylene chloride extracts are washed with brine and dried over anhydrous magnesium sulfate. Evaporation of the solvent in vacuo yields the desired product, 5-dimethylamino-2-chloro-N-[(4-methoxy-6-methyl-1,3,5-triazin-2-yl)aminocarbonyl]benzenesulfonamide.
