反应详情

To a magnetically stirred solution of ethyl 5-methyl-1H-pyrazole-3-carboxylate (3 mmol) in 10 mL of anhydrous DMF at 0° C. is added N-chlorosuccinimide (4 mmol). The solution is stirred at RT for 5 h. The solvent is concentrated to a half of the original volume, water is added and the reaction mixture is allowed to cool over ice. The solid that precipitates is collected by filtration and purified by crystallization to afford 4-chloro-5-methyl-1H-pyrazole-3-carboxylic acid ethyl ester as a white solid: m.p. 106-107° C.; 1H-NMR (DMSO-d6) δ 1.25-1.32 (t, 3H J=7 Hz), 2.21 (s, 3H), 4.22-4.32 (q, 2H J=7.2), 13.59 (s, 1H).

1. concentrationThe solvent is concentrated to a half of the original volume, water
2. additionis added
3. temperatureto cool over ice
4. customThe solid that precipitates
5. filtrationis collected by filtration
6. custompurified by crystallization