反应详情

A solution of 2,4-dioxo-4-phenyl-butyric acid ethyl ester (1.68 g, 0.0076 mole), acetic acid (10 mL) and hydrazine hydrate (0.42 g, 0.0083 mole) was heated to reflux for 5 hours. The reaction mixture was then poured into iced water, basified with saturated aqueous NaHCO3 solution and the product was extracted with ethyl acetate. The ethyl acetate layer was collected and washed with brine solution, dried over sodium and concentrated under reduced pressure. The resulting residue was purified by column chromatography using basic aluminium oxide (50% ethyl acetate in hexane) to afford 1.442 g (88%) of 5-phenyl-1H-pyrazole-3-carboxylic acid ethyl ester. LCMS: 217.09 (M+1)+, 97.92%. To a stirred solution of 5-phenyl-1H-pyrazole-3-carboxylic acid ethyl ester (1.4 g, 0.00667 mol) in a mixture of THF (30 mL), methanol (15 mL) and H2O (10 mL) was added LiOH.H2O (0.839 g, 0.0199 mol) at ambient temperature. The resulting mixture was stirred at 45° C. overnight. Volatiles were evaporated and the residue was diluted with water, acidified with concentrated HCl solution and the product was extracted with ethyl acetate. The ethyl acetate layer was collected, dried over sodium sulfate and concentrated under reduced pressure to afford 1.26 g (86%) of 5-phenyl-1H-pyrazole-3-carboxylic acid. LCMS: 189.06 (M+1)+, 97.7%.

1. temperatureto reflux for 5 hours
2. extractionthe product was extracted with ethyl acetate
3. customThe ethyl acetate layer was collected
4. washwashed with brine solution
5. dry with materialdried over sodium
6. concentrationconcentrated under reduced pressure
7. customThe resulting residue was purified by column chromatography