反应详情

A solution of 5-bromo-4-nitro-2-picoline-N-oxide (30.0 g) in dichloromethane (250 ml) was cooled at 10°, and a solution of phosphoryl chloride (35.5 ml) in dichloromethane (200 ml) added over 15 minutes. The mixture was heated under reflux for 5 hours, allowed to cool to ambient temperature, and allowed to stand for 16 hours. After pouring onto ice (300 ml) and stirring for 15 minutes, the mixture was basified to pH 10 using concentrated aqueous sodium hydroxide. The organic phase was separated off, and the aqueous phase further extracted with chloroform (2×100 ml). The combined organic phases were dried (K2CO3) and stripped to a solid, which was triturated with petroleum ether (40-60), filtered, washed and dried to yield 4-chloro-5-bromo-2-picoline-N-oxide, 24.08 g, m.p. 121°-4° C.

1. temperatureThe mixture was heated
2. temperatureunder reflux for 5 hours
3. additionAfter pouring onto ice (300 ml)
4. customThe organic phase was separated off
5. extractionthe aqueous phase further extracted with chloroform (2×100 ml)
6. dry with materialThe combined organic phases were dried (K2CO3)
7. customwas triturated with petroleum ether (40-60)
8. filtrationfiltered
9. washwashed
10. customdried