2-溴-5-碘甲苯的合成工艺改进

以邻甲苯胺为起始原料,高碘酸钠为氧化剂,单质碘取代得2-氨基-5-碘甲苯,再经重氮化及Gattermann反应,得2-溴-5-碘甲苯,总收率66.1%(以邻甲苯胺计)。结果表明,较佳的工艺条件为:碘化过程中邻甲苯胺、高碘酸钠和碘的摩尔比为1∶0.6∶0.45,反应温度为25～30℃,反应时间3 h;在重氮化、溴代反应中,以亚硝酸钠为重氮化试剂,2-氨基-5-碘甲苯与亚硝酸钠和浓硫酸的摩尔比为1∶1∶7.5,反应温度为0～5℃,溴代反应时间为0.5 h;经精馏所得产物含量超过98%(GC法)。改进后的工艺原料易得,操作简便,适合工业化生产。

Improvement of synthetic process for 2-bromo-5-iodotoluene

2-Bromo-5-iodotoluene was synthesized from o-toluidine by iodination with sodium periodate and I2 to give 2-amino-5-iodotoluene which reacted with sodium nitrite by diazotization,followed by Gattermann reaction with copper powder in 48% hydrobromic acid with an overall yield of 66.1%(based on o-toluidine).The results showed that the optimum process are:in iodination,the molar ratio of o-toluidine,sodium periodate and I2 was 1∶ 0.6 ∶ 0.45,reaction temperature was 25~30 ℃,iodination time was 3 h;in diazotization and bromination,sodium nitrite was used as diazotization reagent,the molar ratio of 2-amino-5-iodotoluene,sodium nitrite and sulfuric acid was 1∶ 1∶ 7.5,reaction temperature was 0~5 ℃,bromination time was 0.5 h,the purity of the target after distilling is more than 98%(GC),the improved process is practical,easy to operate,suitable for industrial production.