Method for synthesizing high-purity levetiracetam
A high-purity, ethyl-based technology, applied in the direction of organic chemistry, can solve the problems of high cost, low yield, harsh reaction conditions, etc., and achieve the effects of low cost, high yield and mild reaction conditions
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Embodiment 1
[0014] 51.3 g of (S)-α-ethyl-2-oxo-1-pyrrolidineacetic acid and 120 mL of dichloromethane were put into a three-necked flask. Cool down to -10°C, add 47.8g of diisopropylethylamine and 35.7g of ethyl chloroformate in sequence, control the temperature at -5°C, and continue the reaction for 30 minutes. Keep the temperature at about -5°C, and react with ammonia gas until the conversion of raw materials is complete. After the reaction was completed, filter and wash the filter cake with dichloromethane. After the filtrate and washing liquid were combined, the residue obtained was concentrated under reduced pressure, recrystallized with 45 mL of ethyl acetate (containing 0.5% diisopropylethylamine), filtered with suction, and dried to obtain (S)-α-ethyl - 43 g of 2-oxo-1-pyrrolidineacetamide, yield 85%. The optical purity is 99.5%, the HPLC purity is 99.6%, and the impurity (S)-α-ethyl-2-oxo-1-pyrrolidineacetic acid content is 0.06%.
Embodiment 2
[0016] Add 55 g of (S)-α-ethyl-2-oxo-1-pyrrolidineacetic acid and 130 ml of dichloromethane into a three-necked flask. Add 51.2 g of diisopropylethylamine and 38.3 g of ethyl chloroformate in sequence, control the temperature at 25° C., and continue the reaction for 30 minutes. Keep the temperature at about 25°C, and react with ammonia gas until the raw materials are completely reacted. After the reaction was completed, filter and wash the filter cake with dichloromethane. The filtrate and washings were combined and concentrated under reduced pressure. The obtained residue was recrystallized by adding 50 mL of ethyl acetate (containing 0.5% triethylamine), suction filtered and dried to obtain (S)-α-ethyl-2-oxo-1-pyrrolidineacetamide 44.7 g. Yield 83%. The optical purity is 99.6%, the HPLC purity is 99.7%, and the impurity (S)-α-ethyl-2-oxo-1-pyrrolidineacetic acid content is 0.07%.
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