反应详情

75 g of phosgene are introduced at a temperature of 85°-95° C. over 1 hour into a mixture of 87.5 g of 5-chloro-2-hydroxy-3-nitropyridine in 500 ml of toluene and 3 ml of N,N-dimethylformamide. The reaction mixture is kept for 2 hours under reflux at 85°-95° C. and then allowed to cool to room temperature over a period of 18 hours. The reaction mixture is washed 3 times with water and the organic phase is dried over sodium sulfate and thereafter concentrated by evaporation. The crude product, obtained in the form of a brown oil, is crystallised from 200 ml of n-hexane, giving 67.5 g of 2,5-dichloro-3-nitropyridine (70% of theory) with a melting point of 38°-39° C.

1. temperatureunder reflux at 85°-95° C.
2. washThe reaction mixture is washed 3 times with water
3. dry with materialthe organic phase is dried over sodium sulfate
4. concentrationconcentrated by evaporation
5. customThe crude product, obtained in the form of a brown oil
6. customis crystallised from 200 ml of n-hexane