Water → 2-(6-Bromo-7-methyl-3-thioxo-2,3-dihydro-benzo[1,4]oxazin-4-yl)-propionic acid ethyl ester

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Reaction Steps

To a solution of 2-(6-bromo-7-methyl-3-oxo-2,3-dihydro-benzo[1,4]oxazin-4-yl)-propionic acid ethyl ester (23.6 g, 69 mmol) in toluene (300 mL) was added Lawesson's reagent (30.7 g, 76 mmol) and the reaction mixture was heated at reflux for 4 h. The reaction mixture was cooled to ambient temperature water (300 mL) was added. The organic phase was separated and the aqueous portion was extracted with EtOAc (3×100 mL). The combined organic phase was washed with brine (100 mL), dried over anhydrous Na2SO4, filtered and concentrated in vacuo. The residue was purified by column chromatography on silica gel (eluting with 5% EtOAc in petroleum ether) to give 2-(6-bromo-7-methyl-3-thioxo-2,3-dihydro-benzo[1,4]oxazin-4-yl)-propionic acid ethyl ester as solid (20.0 g, 81%). 1H NMR (DMSO-d6, 400 MHz): δ 7.41 (s, 1H), 7.16 (s, 1H), 6.03 (m, 1H), 4.90 (s, 2H), 4.14 (m, 2H), 2.29 (s, 3H), 1.61 (d, J=6.8 Hz, 3H), 1.08 (t, J=7.2 Hz, 3H).

Provenance & Evidence