2-苄硫基-5,7-二甲氧基-1,2,4-三唑并[1,5-a]嘧啶的合成研究

Synthesis of 2-benzylthio-5,7-dimethoxy-1,2,4-triazole[1,5-a]pyrimidine.

2-苄硫基-5,7-二甲氧基-1,2,4-三唑并[1,5-a]嘧啶(Ⅲ)是磺草唑胺(metosulam)及1,2,4-三唑[1,5-a]嘧啶醚类超高效除草剂的重要中间体.由5-氨基-3-苄硫基-1,2,4-三唑(Ⅰ)为起始原料,经环合、氯代一步反应制得2-苄硫基-5,7-二氯-1,2,4-三唑并[1,5-a]嘧啶(Ⅱ).优化试验发现90℃、丙二酸与(Ⅰ)摩尔比为1.1∶1、反应20 h时收率达85%以上.(Ⅱ)与甲醇钠进行置换反应制得(Ⅲ),对反应温度和物料配比进行了优化试验,发现25℃、甲醇钠与(Ⅱ)的摩尔比为5∶1时收率达到90%以上.中间体(Ⅱ)、(Ⅲ)的结构经1H-NMR、MSI、R确证.该方法原料易得、操作简便,总收率较高.

2-Benzylthio-5,7-dimethoxy-1,2,4- triazole[ 1,5-a] pyrimidine（ Ⅲ ） is the most important intermediate ol metosulam and 1,2,4-triazolo[- 1,5-a] pyrimidine-2-ether derivatives. 2-Benzylthio-5,7-dichloro-1,2,4 -triazole[- 1,5- a]pyrimidine（ Ⅱ） was synthesized from 5-amino-3-benzyhhio -1,2,4-triazole（ Ⅰ ） by ring closure and chlorination; based on the optimized test of time .temperature and the molar ratio between malonic acid and （ Ⅰ）, （ Ⅱ ） had a yield above 85% with 20 h .the molar ratio above 1.1 ： 1 at 90 ℃ in one step. （ Ⅲ） was prepared from （ Ⅱ） with sodium methylate by metathetical reactions;after the optimized test of temperature and the molar ratio between sodium methylateand （Ⅱ）, （Ⅲ） had ayield above 90% with the molar ratio above 5 ： 1 at 25 ℃. （Ⅱ）.（Ⅲ） were identified by ^1H NMR.MS.IR. This route is simple, the reaction conditions are mild, the raw materials are cheap and easy to obtain.