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

Temperature

55 °C

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%.

1. temperatureThe reaction mixture was cooled
2. customthe solvent was removed under reduced pressure
3. dissolutionThe residual solid was dissolved in ethyl acetate (300 ml)
4. washwashed with water (300 ml)
5. customThe aqueous phase was removed
6. extractionextracted with ethyl acetate (300 ml)
7. dry with materialthe combined organic extracts were dried over MgSO4
8. customThe solvent was removed under reduced pressure
9. customthe residue was azeotroped with dichloromethane (2×50 ml)

ORD record

ord-36066e318f904261947d4be0b081573b

Source dataset

uspto-grants-2005_11

DOI

10.6084/m9.figshare.5104873.v1

Patent number

US06967204B2