反应详情

Potassium t-butoxide (0.51 g, 4.5 mmol) was dissolved in DMSO (10 mL) and to this solution was added ethyl 3-(thiophen-2-yl)-1H-pyrazole-5-carboxylate (1.01 g, 4.5 mmol) in small portions and stirred under Ar for 15 min. To this solution was added 2-iodopropane (1.2 g, 6.8 mmol) slowly and stirred for 1 h at RT. Sat. NH4Cl solution was added, the product was extracted with EtOAc (2×40 mL). The combined organics were washed with brine, dried (Na2SO4) and concentrated in vacuo. Purification by silica gel chromatography provided ethyl 1-isopropyl-3-(thiophen-2-yl)-1H-pyrazole-5-carboxylate as a pasty mass (0.88 g, 73% yield). 1H NMR (400 MHz, Acetone-d6): δ 7.47 (dd, J=3.2 Hz, 1.2 Hz, 1H), 7.42 (dd, J=4.8 Hz, 1.2 Hz, 1H), 7.12-7.09 (m, 2H), 5.57-5.51 (m, 1H), 4.37 (q, J=7.2 Hz, 2H), 1.50 (d, J=6.8 Hz, 6H), 1.38 (t, J=7.2 Hz, 3H); MS (ESI) m/z: 265.0 (M+H+).

1. stirringstirred for 1 h at RT
2. extractionthe product was extracted with EtOAc (2×40 mL)
3. washThe combined organics were washed with brine
4. dry with materialdried (Na2SO4)
5. concentrationconcentrated in vacuo
6. customPurification by silica gel chromatography