反应详情

To a solution of 3-[4-(1-ethoxycarbonyl-ethyl)-3-oxo-3,4-dihydro-2H-benzo[1,4]oxazin-6-yloxy]-azetidine-1-carboxylic acid tert-butyl ester (0.700 g, 1.66 mmol) in toluene (15 mL) and DME (15 mL) was added Lawesson's reagent (1.058 g, 2.66 mmol) and the mixture was heated to reflux for 4 h. The mixture was cooled to ambient temperature and concentrated in vacuo. The residue was purified by column chromatography on silica gel (eluting with 15% EtOAc in petroleum ether) to give 3-[4-(1-ethoxycarbonyl-ethyl)-3-thioxo-3,4-dihydro-2H-benzo[1,4]oxazin-6-yloxy]-azetidine-1-carboxylic acid tert-butyl ester (0.540 g, 74%) as a white solid. 1H NMR (CDCl3, 400 MHz): δ 6.94 (d, J=8.8 Hz, 1H), 6.67 (br, 1H), 6.39 (m, 1H), 6.36 (m, 1H), 4.88 (d, J=15.2 Hz, 2H), 4.74 (m, 1H), 4.27 (m, 2H), 4.19 (m, 2H), 3.97 (m, 2H), 1.68 (d, J=7.2 Hz, 3H), 1.45 (s, 9H), 1.14 (t, J=7.2 Hz, 3H).

1. temperaturethe mixture was heated
2. temperatureto reflux for 4 h
3. concentrationconcentrated in vacuo
4. customThe residue was purified by column chromatography on silica gel (eluting with 15% EtOAc in petroleum ether)