反应详情

2-Amino-5-chloropyrazine (1.7 g) was dissolved in chloroform (190 ml) and pyridine (1.3 ml) was added under an argon atomosphere. The flask and its contents were protected from light and a solution of bromine (0.7 ml) in chloroform (85 ml) was added over a period of 1 hour. After stirring for 2 hours more bromine (0.07 ml) in chloroform (8.5 ml) was added. After stirring for 30 minutes, pyridine (0.2 ml) was added. The reaction mixture was stirred for a further 30 minutes then washed with water (50 ml) and the organic phase was separated. Volatile material was removed by evaporation and and the residue was purified by chromatography through a bed of silica (90 g), eluting with hexane (200 ml), followed by dichloromethane. Dichloromethane fractions containing the product were evaporated to give 2-amino-3-bromo-5-chloropyrazine (1.68 g); 1H NMR (d6 -DMSO): 6.94 (br s, 2H), 8.09 (s, 1H); mass spectrum (+ve CI): 208 (M+H)+.

1. additionwas added
2. stirringThe reaction mixture was stirred for a further 30 minutes
3. washthen washed with water (50 ml)
4. customthe organic phase was separated
5. customVolatile material was removed by evaporation
6. customthe residue was purified by chromatography through a bed of silica (90 g)
7. washeluting with hexane (200 ml)
8. additionDichloromethane fractions containing the product
9. customwere evaporated