Methyl iodide → 1-Methyl-5-methylthio-3-(trifluoromethyl)pyrazole

3.87 g of compound (8-5) and 4.40 g of potassium carbonate were suspended in 100 ml of acetonitrile. The suspension was stirred at room temperature for 15 minutes. A solution of 3.62 g of methyl iodide in 10 ml of acetonitrile was added dropwise, and the mixture was stirred at room temperature for 12 hours. The reaction solution was concentrated under reduced pressure. After water was added to the residue, the mixture was extracted with ethyl acetate. The organic layer was dried over magnesium sulfate, and filtered. The filtrate was concentrated under reduced pressure to produce 3.60 g of 1-methyl-5-methylthio-3-(trifluoromethyl)pyrazole (14).