General procedure for the synthesis of ethyl 3-methyl-1H-pyrazole-4-carboxylate from methanol and 3-methylpyrazole-4-carboxylic acid: 3-methylpyrazole-4-carboxylic acid (1.26 g, 10 mmol) was dissolved in methanol (100 mL) at 0 °C and thionyl chloride (5.73 g, 45 mmol) was added slowly, the reaction mixture was stirred at room temperature for 12 hours. After completion of the reaction, the solvent was removed by vacuum evaporation. The residue was neutralized by adding saturated aqueous sodium bicarbonate solution and the mixture was extracted with ethyl acetate (100 mL x 3). The organic phases were combined, dried with anhydrous sodium sulfate, filtered and the filtrate was concentrated in vacuum to give ethyl 3-methyl-1H-pyrazole-4-carboxylate (0.8 g, 57% yield). The product was characterized by 1H NMR (300 MHz, CDCl3): δ 7.87 (s, 1H), 3.84 (s, 3H), 2.53 (s, 3H).
