反应详情

温度

0 °C

4-Ethoxycarbonyl-2-(4-amino phenyl)-3-pyrazolin-5-one (610 mg, 2.46 mmol) in 5N Sulphuric acid (90 ml) was stirred on a boiling water bath to give a solution. This was cooled to 0° C. and the colloidal precipitate formed treated with sodium nitrite (190 mg, 2.71 mmol) in water (2 ml). The whole was then allowed to stir for 2 hours at 0° C. under nitrogen and then added dropwise to boiling 5N sulphuric acid (30 ml) so as not to interrupt boiling. The solution was then allowed to cool and was extracted with ethyl acetate which, after drying (MgSO4) and evaporation, gave the crude product (190 mg). This was purified by chromatography on silica (hexane; ethyl acetate) to give the desired product (101 mg) νmax (KBr Disc) 1660, 1595, 1520, 1433, 1277, 1140 cm-1, δ(D6 -Acetone) 1.33(3H, t, J7 Hz,--OCH2CH3), 3.30(1H, br), 4.33(2H,q,J7 Hz--OCH2CH3), 6.94 (2H, d, J9 Hz, protons o--OH), 7.65 (2H,d, J9 Hz, protons m--OH), 8.44 (1H, s, C3 pyrazole proton), 8.75 (1H, brs); Found: M+, 248.0773; C12H12N2O4 requires M, 248.0797. Calculated: C,58.1; H,4.8; N,11.3, Found: C, 58.3; H,5.1; N, 11.0

1. customto give a solution
2. customthe colloidal precipitate formed
3. additionadded dropwise
4. temperatureto cool
5. extractionwas extracted with ethyl acetate which
6. customafter drying
7. custom(MgSO4) and evaporation
8. customgave the crude product (190 mg)
9. customThis was purified by chromatography on silica (hexane; ethyl acetate)