4091-39-8

17356-08-0

2289-75-0

1. In a 250 mL three-necked round-bottomed flask equipped with a stirrer, condenser tube, and constant-pressure dropping funnel, 43.27 g (0.6 mol) of 3-chloro-2-butanone and 30.42 g (0.3 mol) of 36% hydrochloric acid were added. Subsequently, 8.1 g (0.06 mol) of copper chloride was added and the reaction system was warmed to 35°C. 49.23 g (0.39 mol) of 30% hydrogen peroxide was added slowly and dropwise over a period of 15 minutes. After the dropwise addition was completed, the reaction mixture was heated to 78°C and refluxed for 5 hours. After completion of the reaction, it was cooled to room temperature, the organic phase was separated, washed twice sequentially with saturated sodium carbonate solution and dried over anhydrous sodium sulfate. The 137-140°C fraction was collected by decompression distillation to give 8.0 g of 3-chloro-2-butanone derivative XVII in 12.6% yield. 2. 30 mL of ethanol and 3.5 g (47 mmol) of thiourea were added to a 100 mL round-bottomed flask and heated to reflux with stirring until the thiourea was completely dissolved. Subsequently, 5.0 g (47 mmol) of 3-chloro-2-butanone derivative XVII was added and refluxing was continued overnight. After completion of the reaction, the ethanol was removed by concentration under reduced pressure. The crude product obtained was dissolved in 30 mL of dichloromethane, washed with saturated sodium carbonate solution, the organic layer was separated and dried over anhydrous sodium sulfate. After concentration, a yellow oil was obtained, which was further processed to give 2-amino-4,5-dimethylthiazole XVIII 3.8 g in 63.3% yield.