反应详情

A suspension of 7-fluoro-6-nitro-4H-benzo[1,4]oxazin-3-one (3.50 g, 16.50 mmol) and K2CO3 (3.42 g, 24.75 mmol) in acetone (100 mL) was stirred at rt for 15 min. A solution of ethyl 2-bromopropanoate (5.97 g, 33.0 mmol) in acetone (60 mL) was added dropwise and the reaction mixture was heated at reflux for 5 h. The reaction mixture was cooled to ambient temperature and concentrated in vacuo. The residue was dissolved in DCM (50 mL) and washed with water (50 mL). The organic phase was separated and dried over anhydrous Na2SO4, filtered and the filtrate was concentrated in vacuo. The residue was purified by column chromatography on silica gel (eluting with 0-30% EtOAc in petroleum ether) to give 2-(7-fluoro-6-nitro-3-oxo-2,3-dihydro-benzo[1,4]oxazin-4-yl)-propionic acid ethyl ester as a white solid (3.29 g, 64%). 1H NMR (DMSO-d6, 400 MHz): δ 7.89 (d, J=7.2 Hz, 1H), 7.39 (d, J=11.6 Hz, 1H), 5.28 (q, J=7.2 Hz 1H), 4.86 (s, 2H), 4.02-4.16 (m, 2H), 1.48 (d, J=7.2 Hz, 3H), 1.12 (t, J=7.2 Hz, 3H).

1. temperaturethe reaction mixture was heated
2. temperatureat reflux for 5 h
3. temperatureThe reaction mixture was cooled to ambient temperature
4. concentrationconcentrated in vacuo
5. dissolutionThe residue was dissolved in DCM (50 mL)
6. washwashed with water (50 mL)
7. customThe organic phase was separated
8. dry with materialdried over anhydrous Na2SO4
9. filtrationfiltered
10. concentrationthe filtrate was concentrated in vacuo
11. customThe residue was purified by column chromatography on silica gel (eluting with 0-30% EtOAc in petroleum ether)