6-羧基-1,2,3-苯并噻二唑的合成研究

Synthesis of 6-Carboxyl-1,2,3-benzothiadiazole

合成了用于诱导植物系统获得抗性的化合物 6 羧基 1,2 ,3 苯并噻二唑 ,其合成步骤如下 :以对氨基苯甲酸 (I)为原料 ,用乙酰酐作为乙酰化试剂 ,在加热回流下反应 4h ,将化合物I的氨基进行保护 ,得对 乙酰氨基苯甲酸 (Ⅱ )。将化合物Ⅱ在 12～ 15℃下缓慢加入到氯磺酸中去进行氯磺化反应 .氯磺酸对化合物Ⅱ的量比为n(氯磺酸 )∶n(对 乙酰氨基苯甲酸 ) =4∶1,反应温度维持在 6 0℃ ,得化合物 2 乙酰氨基 5 羧基苯磺酰氯 (Ⅲ )。以锌粉加醋酸作为还原剂 ,在 70℃下搅拌回流 6h ,将化合物Ⅲ还原为 3 巯基 4 氨基 -苯甲酸 (Ⅳ )。将化合物Ⅳ在 0～ 5℃下用亚硝酸钠加冰醋酸去进行重氮化反应 ,然后用乙醚萃取 ,蒸去溶剂后得红棕色固体产物 6 羧基 1,2 ,3 苯并噻二唑 (V) ,产率 43 %

Carboxyl 1,2,3 benzothiadiazole (V),used as inducer of systemic acquired resistance of plant,was synthesized according to following procedures. p Acetaminobenzoic acid (Ⅱ)which was prepared by reaction of p aminobenzoic acid (I)with acetic anhydride was added slowly into chlorosulfonic acid at 12-15 ℃.The mole ratio of chlorosulfonic acid to Ⅱ was 4∶1.After all Ⅱ was added,the reaction proceeded further at 60 ℃ for 1 h,giving 2 acetamino 5 carboxylbenzenesulfonyl chloride(Ⅲ).Compound Ⅲ was reduced by zinc powder in glacial acetic acid at 20 ℃ under stirring and refluxing for 6 h,to give 3 hydrosulfuryl 4 aminobenzoic acid (Ⅳ).Finally,Ⅳ was diazotized and extracted with ether to afford the title compound V in 43% yield.