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

Participants

Reaction Steps

5-Isobutyl-1H-pyrazol-3-carboxylic acid ethyl ester (16.2 g, 83 mmol) and 1M NaOH solution (173 ml, 173 mmol) were dissolved in 1,4-dioxan (260 ml) and the reaction was stirred at room temperature under nitrogen for 64 hours. The reaction mixture was adjusted to pH 7 using concentrated hydrochloric acid, and concentrated under reduced pressure. Water (500 ml) was added, the slurry was adjusted to pH 1 with concentrated hydrochloric acid and the aqueous phase was extracted with ethyl acetate (5×300 ml). The combined organic extracts were dried over MgSO4 and the solvent was removed under reduced pressure to give 5-isobutyl-1H-pyrazol-3-carboxylic acid (10 g) as a white solid. 1H NMR (400 MHz, DMSO-D6): δ=12.72-12.90 (1H, brs), 6.39 (1H, s), 2.39-2.43 (2H, d), 1.77-1.86 (1H, m), 0.78-0.83 (6H, d) ppm. LRMS (electrospray): m/z [M+Na]+ 191, [2M+Na]+ 359, [M−H]+ 167, [2M−H]+ 335.

Provenance & Evidence