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温度

0 °C

To a mixture of sodium methoxide (8 g) and anhydrous ethanol (100 ml) is added benzamidine hydrochloride (11.7 g) at 0° C. The mixture is stirred at 0° C. for 30 minutes, and thereto is added dropwise a solution of crude ethyl 2-(N,N-dimethylaminomethylene)nitroacetate (14 g, which is obtained by heating a mixture of ethyl nitroacetate (10 g) and N,N-dimethylformamide dimethyl acetal (10.7 g) under reflux for three hours, followed by concentrating the mixture under reduced pressure) in anhydrous ethanol (50 ml) at the same temperature. After the addition, the mixture is stirred at room temperature for 30 minutes, and refluxed for 12 hours. The reaction mixture is concentrated under reduced pressure, and to the resultant is added water (150 ml). To the mixture is added dropwise conc. hydrochloric acid at 0° C. until the pH value of the mixture is adjusted to pH 4. The precipitates are collected by filtration, washed with water, and recrystallized from ethanol to give the desired compound (7 g).

1. customwhich is obtained
2. temperatureby heating
3. temperatureunder reflux for three hours
4. concentrationby concentrating the mixture under reduced pressure) in anhydrous ethanol (50 ml) at the same temperature
5. additionAfter the addition
6. stirringthe mixture is stirred at room temperature for 30 minutes
7. temperaturerefluxed for 12 hours
8. concentrationThe reaction mixture is concentrated under reduced pressure
9. additionto the resultant is added water (150 ml)
10. additionTo the mixture is added dropwise conc. hydrochloric acid at 0° C. until the pH value of the mixture
11. filtrationThe precipitates are collected by filtration
12. washwashed with water
13. customrecrystallized from ethanol