反应详情

Dissolve 3-acetyl-4-oxopentanoic acid ethyl ester (3.35 g, 19.5 mmol) in glacial acetic acid (20 mL) and add methylhydrazine (1.13 mL, 21.4 mmol) dropwise. Stir the resulting mixture at room temperature for 16 hr. Concentrate and partition the residue between ethyl acetate (100 mL) and saturated aqueous sodium bicarbonate solution (50 mL). Separate organic layer, dry (sodium sulfate), filter, concentrate and purify (silica gel chromatography, eluting with 7:3 hexanes:ethyl acetate) to give (1,3,5-trimethyl-1H-pyrazol-4-yl)-acetic acid ethyl ester (2.8 g, 73%) as an oil. 1H NMR (CDCl3) δ 4.08 (q, 2H), 3.67 (s, 3H), 3.29 (s, 2H), 2.18 (s, 6H), 1.21 (t, 3H).

1. concentrationConcentrate
2. custompartition the residue between ethyl acetate (100 mL) and saturated aqueous sodium bicarbonate solution (50 mL)
3. dry with materialSeparate organic layer, dry (sodium sulfate)
4. filtrationfilter
5. concentrationconcentrate
6. custompurify
7. wash(silica gel chromatography, eluting with 7:3 hexanes:ethyl acetate)