4-(methylthio)-1H-pyrazole

2075-45-8

624-92-0

1393128-21-6

Step 1: Synthesis of 4-(methylthio)-1H-pyrazole 4-Bromopyrazole (4 g, 27 mmol) was suspended in tetrahydrofuran (68 mL) and cooled to 0 °C. n-Butyllithium (2.5 M hexane solution, 35.9 mL, 90 mmol) was added dropwise over 20 min. The reaction mixture was stirred at room temperature for 1 hour and then cooled to 0°C again. 1,2-Dimethyl disulfide (2.66 mL, 30.0 mmol) was added dropwise and stirring was continued for 1.5 hours at 0 °C. The reaction mixture was poured into water (150 mL) and acidified with saturated aqueous ammonium chloride and 1N aqueous hydrochloric acid to pH~8. The mixture was extracted with ethyl acetate (150 mL x 3), the organic layers were combined and dried over sodium sulfate. Filtration and concentration under reduced pressure afforded 4-(methylthio)-1H-pyrazole (3300 mg). The product was characterized by 1H NMR (500 MHz, CDCl3): δ 2.36 (s, 3H), 7.63 (s, 2H).