嘧啶与吡啶衍生物硝化方法的改进

Superior Methodology for the Nitration of Pyrimidine and Pyridine Derivatives

目的:改进6-氯-3-甲基脲嘧啶和2-羟基吡啶的硝化方法,分别制备6-氯-3-甲基-5-硝基脲嘧啶和2-羟基-3-硝基吡啶。方法:采用KNO3代替浓硝酸与浓硫酸组成的复合硝化剂分别对两原料进行硝化,同时考察原料与KNO3的摩尔比、加料温度以及反应时间和温度对硝化收率的影响,以确定最佳工艺条件。结果:适宜于6-氯-3-甲基脲嘧啶硝化和制备相应目标产物的反应条件是:原料与硝酸钾的摩尔比为1∶1.25～1∶1.3,加料温度为5℃,反应时间为2h,反应温度为25℃。而适宜于2-羟基吡啶硝化和制备相应目标产物的反应条件基本上与之相同,只是反应温度为45℃～50℃。两个目标产物的收率分别达53%和54%。结论:本方法操作简便,其反应温和、安全、易控,且收率较高。

Objective： To improve the process of the nitration of 6-chloro-3-methyluraeil and 2-hydroxypyridine as starting materials for the synthesis of 6-chloro-3-methyl-5-nitrouracil and 2-hydroxy- 3-nitropyridine. Methods： KNO3-H2SO4 was used as a mixed nitrating agent instead of HNO3-H2SO4 to nitrate the two starting materials respectively. The influences of starting material/KNO3 molar ratio,feeding temperature and nitration time and temperature on the nitration were investigated in order to find out a superior nitrating condition. Results： The conditions suitable for the nitration of 6-chloro-3-methylu- racil into corresponding target product were found as follows： a starting material/KNO3 molar ratio of 1 ： 1.25-- 1 ： 1.3, a feeding temperature of 5 ℃, a nitrating time of 2 h and a nitrating temperature of 25 ℃. The conditions suitable for the nitration of 2-hydroxypyridine into another target product were found substantially ditto except for a nitrating temperature of 45 ℃--50 ℃. The yields of the two target products were 53% and 54% respectively. Conclusion： The improved process is easy to operate in which the nitrating reaction is mild, safe and controllable with the higher yield.