General procedure for the synthesis of 5-chloro-3-methylpyrazole from 5-chloro-1,3-dimethyl-1H-pyrazole: (a) 5-chloro-1,3-dimethylpyrazole (2.6 mmol) and pyridine hydrochloride (13.1 mmol) were placed in a sealed 5 mL process vial, and the mixture was heated by microwave radiation for 2 hr at 200 °C. After completion of the reaction, it was cooled to room temperature, ethyl acetate (15 mL) was added, the mixture was washed sequentially with 2 M aqueous hydrochloric acid (10 mL) and saturated aqueous sodium chloride, dried over anhydrous magnesium sulphate and concentrated to give the title compound 5-chloro-3-methylpyrazole as a white solid (yield: 210 mg, 67%). Mass spectrometry (MS) showed molecular ion peak (M+H) m/z = 117. 1H-NMR (DMSO-d6, 400 MHz) data: δ 12.66 (broad single peak, 1H), 6.03 (multiple peaks, 1H), 2.19 (single peak, 3H).
