General procedure for the synthesis of ethyl (1H-pyrazol-3-yl)acetate from ethanol and 2-(1H-pyrazol-3-yl)acetic acid: 2-(1H-pyrazol-3-yl)acetic acid (4.0 g, 32 mmol) was dissolved in a solution of ethanol (100 mL) containing concentrated HCl, and H2SO4 (1.0 mL) was added as catalyst. The reaction mixture was heated to reflux overnight. After completion of the reaction, the reaction solution was concentrated and the residue was neutralized with aqueous NaHCO3. The aqueous phase was extracted with ethyl acetate and the organic phase was dried with Na2SO4. The solvent was removed under reduced pressure to give ethyl (1H-pyrazol-3-yl)acetate (4.6 g, 94% yield) as a brown oil.LC-MS (ESI): m/z = 155 (M + H)+.
