In the first step, the condensation reaction was carried out. A methanol solution of 270 g of anhydrous methanol and 500 g of sodium methanolate was added to a 2L four-neck flask. Cooled to 0-5 °C in an ice-water bath, 72.8 g of malononitrile was added and stirred for 30 min, keeping the temperature at 0-5 °C. 146.5 g of N-cyanoimido-S,S-dimethyl dithiocarbonate was added in batches and the reaction was stirred at 0-5 °C for 12 hours. The reaction was completed and filtered and the filter cake was washed with 100 mL of cold anhydrous methanol and drained. The wet product was used directly in the next step of the reaction. In the second step, the cyclization reaction was carried out. The above wet product was dissolved in 860 g of water and added to a four-necked flask. After dissolving with stirring, the ice water bath was cooled to 0-5 °C and 1200 g of industrial hydrochloric acid was added slowly and dropwise for about 4-5 hours. The reaction was carried out overnight at 0-5°C. Upon completion, the reaction was filtered and the filter cake was washed twice with 10% sodium carbonate solution and dried to give 157 g of dried product. In the third step, the cyclopropylation reaction was carried out. 315 g of the product of the second step, 1000 g of ethanol and 66.7 g of cyclopropylamine were added to a 2L four-necked flask, stirred and heated to reflux. The reaction was cooled to 0-5°C overnight, filtered, and the filter cake was washed, drained, and dried to give 147 g of dried product. Step 4, oxidation reaction. To a 5L four-necked flask were added 414 g of the third step product, 810 g of acetic acid and 5.5 g of sodium tungstate and heated to 50-55 °C. 230g of hydrogen peroxide was added slowly under stirring, and the reaction was carried out at 50-55°C for 4 hours after the addition. After the reaction was completed, the acetic acid was recovered under reduced pressure, and the residue was cooled to below 10°C with 800g of water, filtered, and the filter cake was washed to pH 5-6, drained, and then used directly in the next step of the reaction. The fifth step, ammoniation reaction. Add the product of the fourth step, 610g of ethanol and 1450g of ammonia in a 5L four-necked flask and stir at 20-25°C for 5 hours. After the reaction was completed, it was cooled to 5-10°C, filtered, and the filter cake was washed and dried to obtain 88g of dried product. The 88g of dry product was dissolved in 560mL of N,N-dimethylformamide and heated to 90°C to dissolve. 5g of powdered activated carbon was added, stirred for 10 minutes, filtered, cooled and refrigerated overnight. Filtered on the next day, the filter cake was washed with deionized water, drained and dried to obtain 80g of white powder.
