反应详情

156 mmol (20 g) 2-chloro-6-methylpyrazine were dissolved in 80 ml 96% sulfuric acid, 222 mmol (63 g) potassium peroxodisulfate were added portion wise at 10° C. and stirring was carried out for 2 days at 10° C. and 1 day at room temperature (see also C. E. Mixan, R. Garth, J. Org. Chem. 1977, 42, 1869-1871). The reaction mixture was poured on 200 g ice, under addition of ethanol neutralization was carried out with calcium hydroxide, then filtered off and washed with ethanol. The filtrate was evaporated until dryness, the obtained solid (20 g) were refluxed in 300 ml 20% KOH solution for 3 h and after cooling pH 3 was adjusted with 20% HCl. The solution was evaporated until dryness, the residue boiled with 0.2 l ethanol under reflux for 2 h, after cooling filtered and the filtrate evaporated until dryness. After recrystallization from ethanol/tetrahydrofuran from 7.4 g raw product 2.17 g (10% yield, 93% purity) of the title compound were obtained.

1. filtrationfiltered off
2. washwashed with ethanol
3. customThe filtrate was evaporated until dryness
4. temperaturethe obtained solid (20 g) were refluxed in 300 ml 20% KOH solution for 3 h
5. temperatureafter cooling pH 3
6. customThe solution was evaporated until dryness
7. temperatureunder reflux for 2 h
8. temperatureafter cooling
9. filtrationfiltered
10. customthe filtrate evaporated until dryness