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With sulfuric acid; In methanol; for 20.0h;Reflux;
To a stirred solution of l-methyl-1H-pyrazole-5-carboxylic acid (58, 1g, 7.9mmol) in methanol (16 mL) was added sulfuric acid (0.42mL, 7.9mmol) and the reaction mixture was refluxed for 20 hours. Volatiles were removed under vacuum and the residue was dissolved with EtOAc. The solution was washed with sat. NaHCO3, brine sequentially, dried over anhydrous sodium sulfate and concentrated to provide the title compound methyl 1-methyl-1H-pyrazole-5- carboxylate (59, 0.76 g, 68% yield) 1H-NMR (CHCl3-d, 400 MHz): δH 3.88 (3H, s), 4.19 (3H, s), 6.83 (1H, d, J = 2.0 Hz), 7.46 (1H, d, J = 2.0 Hz).). MS (m/z): 141.1 [M+H]+.