3,6-二氯水杨酸的合成研究

Synthesis of 3,6-Dichlorosalicylic Acid

标题化合物是一种重要的医药中间体,也是合成高效、低毒除草剂麦草畏的关键中间体。以廉价易得的2,5-二氯硝基苯为初始原料,经过水合肼还原、重氮化反应合成2,5-二氯苯酚,再在高温高压下进行羧基化反应合成标题化合物。通过单因素实验,研究了以上反应的关键影响因素,得到了适宜的合成条件,标题化合物的收率65.8%(以2,5-二氯硝基苯计),纯度99.24%,满足应用要求。该合成方法简单经济,产物纯度高、易于分离,收率较高。产物和中间体经过红外光谱和核磁共振波谱分析,表明其特征与标准物一致。

3,6-Dichlorosalicylic acid is a kind of important pesticide intermediate. It is also a key intermediate for production of herbicide dicamba. The route to synthesize the 3,6-dichlorosalicylic acid is determined. The cheap and easy gained 2,5-dichloronitrobenzene were choosed as initial raw materials. The intermediate 2,5-dichlorophenol was obtained via the hydrazine hydrate reduction and the diazotization reaction. Then the target product 3,6-dichlorosalicylic acid is obtained via carboxylation reaction by high temperature and pressure. The key reaction factors are investigated through single factor experiments,and optimum condition is obtained. The yield（ calculated by 2,5-dichloronitrobenzene） and the purity of 3,6-dichlorosalicylic acid is 65. 8% and99. 24%,respectively,and quality satisfies the commercial requirement. The synthetic method is simple and economic,and the target product has high purity and easy separated. The structure of 3,6-dichlorosalicylic acid was confirmed via IR and1 HNMR.