Hydrochloric Acid → 5-(propan-2-yl)-1H-pyrazole-3-carboxylic acid

Participants

Reaction Conditions

Reaction Steps

5-Isopropyl-1H-pyrazol-3-carboxylic acid ethyl ester (18.9 g, 104 mmol) and 1M NaOH solution (260 ml, 259 mmol) were dissolved in 1,4-dioxan (300 ml), the reaction was heated to 50° C. under nitrogen and stirred for 3 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 azeotroped with toluene (2×30 ml), dissolved in ethyl acetate (500 ml) and washed with water (200 ml). The aqueous phase was removed, extracted with ethyl acetate (2×200 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-isopropyl-1H-pyrazol-3-carboxylic acid (14.7 g) as a white solid. 1H NMR (400 MHz, DMSO-D6): δ=12.50-13.30 (2H, brs), 6.42 (1H, s), 2.84-2.94 (1H, quin), 1.15-1.19 (6H, d) ppm. LRMS (electrospray) m/z [M−H]+ 153.

Provenance & Evidence