Synthesis of 2,4-Dichloro-5-sulfamoylbenzoic Acid

2,4-Dichloro-5-sulfamoylbenzoic acid(1)was synthesized by sulfochlorination, ammoniation and hydrolysis with 2,4-dichlorobenzoic acid as raw materials, and the reaction conditions were optimized. The optimum reaction conditions obtained were as follows: the molar ratio of n(HSO_3Cl)∶n(2,4-dichloro benzoic acid)=3.5∶1; reaction temperature was 130~140 °C ,reaction time was 3.5 h.The intermediate 2,4-dichloro-5-(chlorosulfonyl)benzoic acid(2)was abtained. Then the mixturc of n(ammonia)∶n(2)=4∶1was reacted at 10~15 °C for 3 h and acidified with HCl to give (1)with a total yield of 79.3% and purity of 98.7%(HPLC).The structure of the product was confirmed by IR and ~1H NMR.