Hydrochloric Acid → 5-Butyl-1H-pyrazole-3-carboxylic acid

Participants

Reaction Conditions

Reaction Steps

5-Butyl-1H-pyrazol-3-carboxylic acid ethyl ester (24 g, 122 mmol) and 1M NaOH solution (305 ml, 306 mmol) were dissolved in 1,4-dioxan (300 ml), the reaction was heated to 55° C. under nitrogen and stirred for 2 hours. The reaction mixture was cooled, adjusted to pH 2 using concentrated hydrochloric acid and the solvent was removed under reduced pressure. The residual solid was dissolved in ethyl acetate (300 ml) and washed with water (300 ml). The aqueous phase was removed, extracted with ethyl acetate (300 ml) and the combined organic extracts were dried over MgSO4. The solvent was removed under reduced pressure and the residue was azeotroped with dichloromethane (2×50 ml) to give 5-butyl-1H-pyrazol-3-carboxylic acid (22.6 g) as a white solid. 1H NMR (400 MHz, DMSO-D6): δ=12.50-13.00 (2H, brs), 6.41 (1H, s), 2.47-2.57 (2H, t), 1.46-1.56 (2H, quin), 1.19-1.29 (2H, sext), 1.15-1.19 (3H, t) ppm. LRMS (electrospray): m/z [M−H]+ 167. Anal. Found C, 57.01; H, 7.23; N, 16.50. C8H12N2O2 requires C, 57.13; H, 7.19; N, 16.66%.

Provenance & Evidence