A process for preparing 5-methylisoxazole-4-carboxylic-(4′-trifluoromethyl)-anilide comprising: (a) reacting ethylacetoacetate, triethylorthoformate, and acetic anhydride at a temperature of from about 75° C. to about 150° C., to form ethyl ethoxymethyleneacetoacetic ester; (b) combining the ethyl ethoxymethyleneacetoacetic ester with sodium acetate or a salt of trifluoroacetic acid in the presence of hydroxylamine sulfate at a temperature of from about −20° C. to 10° C., to form ethyl-5-methylisoxazole-4-carboxylate; (c) reacting the ethyl-5-methylisoxazole-4-carboxylate with a strong acid to form 5-methylisoxazole-4-carboxylic acid; (d) reacting the crystallized 5-methylisoxazole-4-carboxylic acid with thionyl chloride to form 5-methylisoxazole-4-carbonyl chloride; and (e) reacting the 5-methylisoxazole-4-carbonyl chloride with trifluoromethyl aniline and an amine base at a temperature of from about 0° C. to about 50° C. to form 5-methylisoxazole-4-carboxylic-(4′-trifluoromethyl)-anilide. The process of the invention is especially advantageous for preparing 5-methylisoxazole-4-carboxylic-(4′-trifluoromethyl)-anilide, since the process: (1) eliminates or reduces the formation of the by-product 2-cyanoacetoacetic-1-(4′-trifluoromethyl)-anilide (CATA), generally as low as 0.0006%; (2) eliminates or reduces the formation of isomeric impurity ethyl-3-methyisoxazole-4-carboxylate and its corresponding acid as low as 0.1%, (3) produces a high quality of 5-methylisoxazole-4-carboxylic-(4′-trifluoromethyl)-anilide generally having 99.8-100% HPLC potency; and (4) does not require distillation of the isoxazole ester.
制备5-甲基异噁
唑-4-羧酸-(4'-三
氟甲基)-
苯胺的过程包括:(a)在约75°C至约150°C的温度下,将
乙酰乙酸乙酯、三乙基正
甲酸酯和
乙酸酐反应,形成
乙酸乙酯亚甲基乙酮
乙酸酯;(b)将
乙酸乙酯亚甲基乙酮
乙酸酯与
乙酸钠或
三氟乙酸盐在氢氧胺
硫酸存在下,在约-20°C至10°C的温度下反应,形成
乙酸-5-甲基异噁
唑-4-羧酸酯;(c)将
乙酸-5-甲基异噁
唑-4-羧酸酯与强酸反应,形成5-甲基异噁
唑-4-羧酸;(d)将结晶的5-甲基异噁
唑-4-羧酸与
氯化
亚硫酸形成
5-甲基异噁唑-4-羰基
氯化物;(e)将
5-甲基异噁唑-4-羰基
氯化物与三
氟甲基
苯胺和胺碱在约0°C至约50°C的温度下反应,形成5-甲基异噁
唑-4-羧酸-(4'-三
氟甲基)-
苯胺。该发明的过程特别有利于制备5-甲基异噁
唑-4-羧酸-(4'-三
氟甲基)-
苯胺,因为该过程:(1)消除或减少了副产物2-
氰基乙酮
乙酸-1-(4'-三
氟甲基)-
苯胺(CATA)的生成,通常低至0.0006%;(2)消除或减少了异构杂质
乙酸-3-甲基异噁
唑-4-羧酸酯及其对应酸的生成至0.1%;(3)产生高品质的5-甲基异噁
唑-4-羧酸-(4'-三
氟甲基)-
苯胺,通常具有99.8-100%的HPLC纯度;(4)不需要对
异噁唑酯进行蒸馏。