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With sodium hydroxide; In methanol; at 20℃; for 2h;
To a solution of 1-3 (3.4 g, 15.9 mmol) in MeOH (40 mL) was added NaOH (140 mL, 4M). The reaction mixture was stirred at room temperature for 2 hours. The reaction mixture was concentrated under reduced pressure to remove MeOH. The aqueous phase was acidified with aqueous HCl (1 M) till pH=3 and the mixture was extracted with EtOAc, dried with anhydrous Na2SO4, filtered and concentrated to give the crude product. The crude product was purified by silica gel chromatography eluted to give product 1-4 (2.4 g, 80.4%). MS m/z [ESI]: 189.1 [M+1].
With sodium hydroxide; In methanol; at 20℃; for 0.5h;
A solution of the ester 3 (0.1 g, 0.46 mmol) in MeOH (4 mL) was treated with 4 N NaOH (4 mL) and stirred at rt for 30 min. Later methanol was removed in vacuo and adjusted to pH 2-3 with aq1 N HCl and extracted with EtOAc. The organic layer was dried over anhydrous sodium sulfate and evaporated to get acid 4.
To a solution of compound 29b (2.6 g, 9.1 mmol) in MeOH(30 mL) and H2O (15 mL) was added LiOHH2O (0.5 g, 20.0 mmol) and the mixture was stirred at70 C for 8 h. The reaction mixture was evaporated and H2O (15 mL) was added, then acidified byhydrochloric acid (1 M) to pH 3. The suspension was filtered and washed by H2O (10 mL), driedat 50 C for 4 h to afford 11b as a white solid (2.1g, 89.5% yield), m.p.: 227-229 C, decomposition.1H-NMR: 13.39 (s, 1H), 7.83 (m, 2H), 7.41-7.45 (m, 2H), 7.31-7.35 (m, 1H), 7.18(s, 1H). HRMS(ESI)calcd. For C10H8ClN2O2+: [M + H]+ m/z: 189.0659, found: 189.0659. The 1H-NMR data were in goodagreement with those reported [26].
89.5%
Ethyl 2,4-dioxo-4-phenylbutanoate (16b) (2.6 g, 9.1 mmol)Dissolved in 30mL of methanol, added 15mL lithium hydroxide monohydrate(0.5 g, 20.0 mmol) in water. The reaction was heated to 70 ° C until the hydrolysis was complete. Concentration under reduced pressure gave a solid suspension. 15 mL of water was added and the pH was adjusted to 3 with 1 N diluted hydrochloric acid. Filtering,The title compound 5-phenyl-1H-pyrazole-3-carboxylic acid (Intermediate 16) was obtained.Dark white solid (2.1 g, yield 89.5percent).
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