反应详情

温度

0 °C

To cool DMF (50 mL) at 0° C., POCl3 (30 mL) was added dropwise over 30 minutes, and maintained at 0° C. for 1 hour. To the mixture was added butan-2-one semicarbazone (10 g, 78 mmol) in portions at 70° C. and maintained at 70° C. for 4 hours. The mixture was poured into crushed ice (700 g), neutralized using 10% NaOH solution and extracted using ethyl acetate (3×100 mL). The combined organic layers were washed with water (2×80 mL), saturated aqueous NaCl (100 mL), dried over anhydrous Na2SO4 and concentrated to obtain a crude product, which was purified by column chromatography (60-120 mesh silica gel) using 3-5% methanol in chloroform as eluents to afford 3-ethyl-1H-pyrazole-4-carbaldehyde (1.5 g, 16%) as solid. 1H NMR (CDCl3) δ 9.95 (s, 1H), 8.0 (s, 1H), 3.0 (q, 2H), 1.35 (t, 3H).

1. temperaturemaintained at 70° C. for 4 hours
2. additionThe mixture was poured
3. extractionextracted
4. washThe combined organic layers were washed with water (2×80 mL), saturated aqueous NaCl (100 mL)
5. dry with materialdried over anhydrous Na2SO4
6. concentrationconcentrated
7. customto obtain a crude product, which
8. customwas purified by column chromatography (60-120 mesh silica gel)