反应详情

2-Amino-5,6-dichlorobenzimidazole (3 g, 16 mmole) was suspended in 150 ml of water and brought into solution with 2 ml of HBr. Sodium nitrite (3.3 g, 55 mmole) was then added and the mixture was stirred at room temperature for 1 hr. Excess CuBr2 was then added and the mixture was heated on a steam bath for 1 hr. The aqueous solution was extracted with ethyl acetate (3×100 ml), dried with MgSO4, concentrated, and crystallized from ethyl ether to give 1.13 g (26%) of 2-bromo-5,6-dichlorobenzimidazole (7).

1. temperaturethe mixture was heated on a steam bath for 1 hr
2. extractionThe aqueous solution was extracted with ethyl acetate (3×100 ml)
3. dry with materialdried with MgSO4
4. concentrationconcentrated
5. customcrystallized from ethyl ether