Methyl iodide → 3-(2,6-Dichloro-4-trifluoromethylphenyl)-1-methyl-5-methylsulfenylpyrazole

A suspension of 0.5 g of 3-(2,6-dichloro-4-trifluoromethylphenyl)-5-mercapto-1-methylpyrazole (2), 2.3 g of methyl iodide and 0.4 g of anhydrous potassium carbonate in 10 ml of acetonitrile was refluxed overnight with stirring. The reaction mixture was cooled to room temperature and filtered through Celite, and the filtrate was concentrated under reduced pressure. The residue was purified by chromatography on silica gel to obtain 0.51 g of the desired product in the form of white crystals.