Pyridine → 5-Acetamido-3-bromo-1-(2,6-dichloro-4-trifluoromethylphenyl)pyrazole

Pyridine (4.0 ml) was added dropwise to a stirred solution of 5-amino-3-bromo-1-(2,6-dichloro-4-trifluoromethylphenyl)-pyrazole (5.0 g), acetyl chloride (3.0 g) and dry chloroform (30 ml), causing an exothermic reaction (maximum temperature 60° C.). The reaction mixture was stirred at laboratory temperature for 2h and evaporated to dryness. The residue was dissolved in ethanol (25 ml), ammonia solution (d. 0.880; 25 ml) was added, and the solution was boiled under reflux for 1 h. The cooled reaction mixture was evaporated to dryness, dissolved in dichloromethane (100 ml), washed with dilute hydrochloric acid (3×50 ml) and water (50 ml), dried over anhydrous magnesium sulphate, filtered, and evaporated to give 5-acetamido-3-bromo-1-(2,6-dichloro-4-trifluoromethylphenyl)-pyrazole (5.3 g), m.p. 180-187° C., in the form of a pale brown solid.