Water → 1,5-Dimethyl-3-ethoxycarbonylpyrazole

참여 물질

반응 단계

Ethyl 2,4-dioxovalerate (5.6 ml, 40 mM) was dissolved in glacial acetic acid (35 ml) before cooling the-reaction temperature to 8-10° C. Methylhydrazine (2.0 ml, 38 mM) was added dropwise so that the reaction temperature did not rise above 15° C. After stirring at room temperature for 90 minutes the reaction was poured into ethyl acetate and water. The organic phase was washed with saturated sodium bicarbonate solution, water and brine before drying (MgSO4). Purification was accomplished was by chromatography on silica gel (10×4.5 cm) loading in dichloromethane and eluting with 50% ethyl acetate in hexane. Evaporation of solvent gave the title compound as a coloured oil which crystallised on standing (4.69 g); υmax (CH2Cl2) 1717 and 1223 cm−1; δH (CDCl3) 1.39 (3H, t, J 7.13 Hz), 2.30 (3H, s), 3.85 (3H, s), 4.39 (2H, q, J 7.21 Hz), 6.57 (1H, s); E.I. m/e 168 (25%).

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