27603-25-4

65439-30-7

27603-25-4

General procedure for the synthesis of 2-trifluoromethyl-5-methylsulfinyl-1,3,4-thiadiazole from 2-trifluoromethyl-5-methylsulfinyl-1,3,4-thiadiazole: 1. Preparation of experimental setup: Equipped with reflux condenser, constant pressure dropping funnel, 500 mL three-necked flask (equipped with XO-SM100 ultrasonic-microwave combined reaction system, which is straight into the three-necked flask). 2. Reaction mixture preparation: 150 mL of toluene as solvent, 50 g of 2-methylthio-5-trifluoromethyl-1,3,4-thiadiazole (TDA) at 99.5%, 0.3 g of sodium chlorite and 0.1 g of sodium tungstate composite oxidation catalyst, and 40 g of 35% hydrogen peroxide were added to the three-neck flask. 3. Ultrasonic reaction stage: YCFS201-1500 model ultrasonic reactor (produced by Hangzhou Yuancheng Ultrasonic Technology Co., Ltd.) was used, the ultrasonic power was set at 800 W, the reaction temperature was set at 60°C (temperature fluctuation less than 3°C), and the temperature was precisely controlled by an external heat exchanger. The heat exchanger system was equipped with two sets (high temperature system set at 60℃, low temperature system set at 5℃), and the heat transfer medium was liquid paraffin. The reaction time was 8 minutes. 4. Microwave-ultrasonic combined reaction stage: After the reaction was slightly cooled, 20 g of 70% hydrogen peroxide was slowly added to the three-necked flask. The three-necked flask was directly connected to the XO-SM100 ultrasonic microwave combined reaction system (Nanjing First European Instrument System Manufacturing Co., Ltd.), and the ultrasonic power was set to 600 W and the microwave reaction power to 800 W. The reflux reaction was carried out, and the reaction time was 10 minutes. The reaction time was 10 min. The amount of TDA-sulfoxide intermediate was 0.4% after completion of the reaction as determined by liquid chromatography. 5. Isolation and purification of products: The reaction solution was cooled in an ice-water bath until crystals precipitated, and the target product 2-methylsulfonyl-5-trifluoromethyl-1,3,4-thiadiazole (TDA-sulfone) was obtained as pure white flaky crystals by diafiltration. The mother liquor was concentrated and recrystallized, and the crystalline products were combined to give 55.1 g of TDA-sulfone in 95% yield and 99.6% purity of the liquid phase (the by-product TDA-sulfoxide content was 0.07%).