反应详情

温度

90 °C

A solution of 20 g (78 mmol) of 2,6-dibromopyridine 1-oxide is warmed to 40° C. in 70 ml of H2SO4. Nitrating acid (70 ml of H2SO4 and 34 ml of fuming HNO3) is added to the solution at this temperature. The reaction mixture is heated at 90° C. for 3 h. After cooling, the reaction mixture is poured into 800 ml of ice-water. The solid which has precipitated out is filtered off and washed with water. After drying, the 2,6-dibromo-4-nitropyridine 1-oxide (17.9 g) is suspended in 200 ml of chloroform, 6 ml of phosphorus tribromide (64 mmol) are added at room temperature, and the mixture is stirred for 1 h and then heated under reflux for 2 days. After cooling, the solution is poured into 500 ml of ice-water, and the mixture is neutralised using solid NaHCO3. The aqueous phase is separated off and extracted a number of times with CHCl3, and the combined organic phases are washed with a sodium thiosulfate solution and then with water, dried and evaporated. The residue is recrystallised from EtOH. Yield: 41.7 g (148 mmol), 70% of theory.

1. temperatureAfter cooling
2. customThe solid which has precipitated out
3. filtrationis filtered off
4. washwashed with water
5. customAfter drying
6. temperatureheated
7. temperatureunder reflux for 2 days
8. temperatureAfter cooling
9. customThe aqueous phase is separated off
10. extractionextracted a number of times with CHCl3
11. washthe combined organic phases are washed with a sodium thiosulfate solution
12. dry with materialwith water, dried
13. customevaporated
14. customThe residue is recrystallised from EtOH