Pyrazole-3-carboxylic acid (1.112 g, 10 mmol) was dissolved in ethanol (50 mL) at 80 °C, followed by slow addition of concentrated sulfuric acid (2 mL). The reaction mixture was kept under stirring for 2 hours. Upon completion of the reaction, ethyl 1H-pyrazole-3-carboxylate (1.350 g, 9.6 mmol, 96% yield) was obtained.
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