反应详情

To a solution of 3-bromo-6-chloropicolinic acid (21, 8.0 g, 33.83 mmols) in a mixture of toluene (80 mL) and ethanol (40 mL) was added sulfuric acid (0.66 mL, 6.76 mmols). The reaction mixture was refluxed for 16 h, then allowed to cool, and partitioned between CHCl3 (200 mL) and saturated aq. NaHCO3 (250 mL). The aqueous layer was extracted with CHCl3 (2×100 mL), and the combined organic layers were dried over Na2SO4, filtered, and concentrated to give crude product which was purified by column chromatography (Silica gel 10% EtOAc in hexane) to yield title compound 22 (9.0 g, quantitative) as transparent oil. 1H NMR 400 MHz (DMSO-d6) δ: 8.31 (d, J=8.6 Hz, 1H), 7.68 (d, 1H, J=8.2 Hz), 4.39 (q, J=7.0 Hz, 2H), 1.33 (t, J=7.2 Hz, 3H).

1. temperatureThe reaction mixture was refluxed for 16 h
2. temperatureto cool
3. custompartitioned between CHCl3 (200 mL) and saturated aq. NaHCO3 (250 mL)
4. extractionThe aqueous layer was extracted with CHCl3 (2×100 mL)
5. dry with materialthe combined organic layers were dried over Na2SO4
6. filtrationfiltered
7. concentrationconcentrated
8. customto give crude product which
9. customwas purified by column chromatography (Silica gel 10% EtOAc in hexane)