反应详情

Ethyl 5-amino-1-(4-fluorophenyl)pyrazole-4-carboxylate (5.4 g) was dissolved in 12N hydrochloric acid, and aqueous solution (10 ml) containing sodium nitrite (4.5 g) was added dropwise thereto under ice-cooling, which was followed by stirring for 2 h. An aqueous solution (10 ml) containing copper(I) chloride (10.7 g) was added and the mixture was stirred for 30 min. The mixture was warmed to room temperature and stirred further for 2 h. Solid was filtered off with Celite and ethyl acetate was added to the filtrate to separate the organic layer. The organic layer was washed with saturated brine and dried over anhydrous magnesium sulfate, after which the solvent was evaporated under reduced pressure. n-Hexane was added to the obtained residue to allow crystallization. The crystals were recrystallized from a mixed solvent of ethyl acetate-n-hexane to give ethyl 5-chloro-1-(4-fluorophenyl)pyrazole-4-carboxylate (3.5 g), melting point: 70–72° C.

1. additionwas added dropwise
2. temperatureunder ice-cooling
3. additionwas added
4. stirringthe mixture was stirred for 30 min
5. stirringstirred further for 2 h
6. filtrationSolid was filtered off with Celite and ethyl acetate
7. additionwas added to the filtrate
8. customto separate the organic layer
9. washThe organic layer was washed with saturated brine
10. dry with materialdried over anhydrous magnesium sulfate
11. customafter which the solvent was evaporated under reduced pressure
12. additionn-Hexane was added to the obtained residue
13. customcrystallization
14. customThe crystals were recrystallized from a mixed solvent of ethyl acetate-n-hexane