反应详情

A solution of 2-(6-nitro-3-oxo-2,3-dihydro-benzo[1,4]oxazin-4-yl)-propionic acid ethyl ester (185.0 g, 630 mmol) and Lawesson's reagent (279.4 g, 690 mmol) in toluene (1.5 L) was heated to 120° C. for 3 h. The reaction mixture was cooled to ambient temperature and the solvent was removed in vacuo to give the crude product which was purified by chromatography on silica gel (eluting with 5% EtOAc in petroleum ether) to give 2-(6-nitro-3-thioxo-2,3-dihydro-benzo[1,4]oxazin-4-yl)-propionic acid ethyl ester (133.0 g, 72%) as a yellow liquid. 1H NMR (CDCl3, 400 MHz): δ 8.02 (dd, J=2.4 Hz, J=8.8 Hz, 1H), 7.85 (d, J=2.4 Hz, 1H), 7.15 (d, J=8.8 Hz, 1H), 6.70 (m, 1H), 5.07 (d, J=15.2 Hz, 2H), 4.28 (q, J=7.2 Hz, 2H), 1.75 (d, J=7.6 Hz, 3H), 1.24 (t, J=7.2 Hz, 3H).

1. customthe solvent was removed in vacuo
2. customto give the crude product which
3. customwas purified by chromatography on silica gel (eluting with 5% EtOAc in petroleum ether)