Water → 1-Ethyl-5-methyl-1H-pyrazole-3-carboxylic acid

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Reaction Steps

Ethyl 1-ethyl-5-methylpyrazole-3-carboxylate (10.93 g) in ethanol (70 ml) was treated with KOH (3.69 g), followed by water (30 ml), and the mixture was stirred and heated under reflux for 6 h. The ethanol was removed using a rotary evaporator and ethyl acetate/water were added. The pH of the mixture was adjusted to 3.0 and the layers were separated. The aqueous layer was re-extracted with ethyl acetate. The combined ethyl acetate layers were extracted with excess aqueous NaHCO3. The NaHCO3 extract was poured into excess acid, and the pH was then adjusted to 3, and NaCl was added to the solution. The mixture was then repeatedly extracted with ethyl acetate, and the combined extracts were dried (MgSO4) and evaporated. The residue was triturated with diethyl ether to give the acid as a solid (5.65 g) υmax (CH2Cl2) 2754, 2598, 1698, 1498, 1464, 1387, and 1233 cm−1; δ(CDCl3) 1.40 (3H, t, J 7.3 Hz), 2.32 (3H,s), 4.19 (2H, q, J 7.3 Hz), 6.61 (1H,s) ppm; (Found m/z 154.0740. C7H10N2O2 requires m/z 154.0742).

Provenance & Evidence