砜吡草唑的合成工艺研究

Study on the synthesis process of pyroxasulfone

为了改进除草剂砜吡草唑的合成工艺,以3,3-二甲基丙烯酸乙酯为原料,经环化和氯化反应制得3-氯-5,5-二甲基-4,5-二氢异噁唑,之后与硫脲反应,得到5,5-二甲基-4,5-二氢异噁唑-3-硫基甲脒盐;以三氟乙酰乙酸乙酯为原料,经过环化、羟甲基化、O-二氟甲基化以及取代、氯化制得N-甲基-3-三氟甲基-4-氯甲基-5-二氟甲氧基吡唑;最后,通过取代、氧化得到3-[(5-(二氟甲氧基)-1-甲基-3-(三氟甲基)吡唑-4-基)-甲基磺酰]-4,5-二氢-5,5-二甲基-1,2-异噁唑(砜吡草唑),含量>99%,合成路线总收率>35%。该合成工艺减少了原生产过程中产生的三废,提高了生产效率,有利于砜吡草唑的工业化生产。

In order to improve synthetic process of pyroxasulfone,3-chloro-5,5-dimethyl-4,5-dihydroisoxazole was prepared by cyclization and chlorination using ethyl 3,3-dimethacrylate as a raw material,and then reacted with thiourea to obtain 5,5-dimethyl(4,5-dihydroisoxazol-3-yl)thiocarboxamidine hydrochloride.4-(chloromethyl)-5-(difluoromethoxy)-1-methyl-3-(trifluoromethyl)-1H-pyrazole was prepared by using ethy 4,4,4-trifluoroacetoacetate as a raw material through cyclization,methylolation,difluoromethylation,and substitution chlorination.Finally,pyroxasulfoneis was obtained through substitution and oxidation reactions with the content greater than 99%,and the total yield 35%.The synthetic process reduced the contamination during the production process and improved the production efficiency,which was beneficial to the industrial production of pyroxasulfone.