反应详情

The product from paragraph (h) (5.7 g) in hydrobromic acid (48%; 50 ml) was cooled to -15° C. to -10° C. and bromine (2.6 ml) was added dropwise with stirring. The temperature was then kept at -5° C. to 0° C. while sodium nitrite (5.53 g) in water (12 ml) was added dropwise over a period of 45 minutes. When addition was complete, the mixture was stirred a further 30 minutes at 0° C. and poured on to ice. The mixture was made slightly alkaline by dropwise addition of concentrated ammonia, keeping the temperature at 0° C. with added ice. The mixture was extracted with ether (150 ml). The ether extract was washed with water, sodium bisulphite solution, and water, and then dried and evaporated. The residue was taken up in petroleum (b.p. 40°-60° C.) and the solution filtered and evaporated. The residue was identified as 2-bromo-3-chloro-5-methylpyridine.

1. additionwas added dropwise over a period of 45 minutes
2. additionWhen addition
3. stirringthe mixture was stirred a further 30 minutes at 0° C.
4. additionpoured on to ice
5. customat 0° C.
6. extractionThe mixture was extracted with ether (150 ml)
7. extractionThe ether extract
8. washwas washed with water, sodium bisulphite solution, and water
9. customdried
10. customevaporated
11. filtrationthe solution filtered
12. customevaporated