5-(2-thienyl)-3-isoxazole acid was prepared as follows: 5-(2-thienyl)-3-isoxazole acid methyl ester 20.9g (0.1 mol) was dissolved in 100mL of tetrahydrofuran, 100mL of methanol was added, and lithium hydroxide 8.4g was added and then stirred at room temperature for 2-3h. Gradually, a solid precipitated, and a light red solid was obtained by diafiltration after the reaction was completed. Dissolve the light red solid in water, add dilute hydrochloric acid, adjusted to weak acidity, extracted with ethyl acetate for 2 times, the extract was dried with anhydrous sodium sulfate. The ethyl acetate was evaporated and 17.74g of white solid was obtained with 91% yield.
