Lawesson's reagent → (R)-2-(6-nitro-3-thioxo-2,3-dihydro-benzo[1,4]oxazin-4-yl)-propionic acid ethyl ester

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Reaction Conditions

Reaction Steps

A mixture of (R)-2-(6-nitro-3-oxo-2,3-dihydro-benzo[1,4]oxazin-4-yl)-propionic acid ethyl ester (80.0 g, 272.0 mmol) and Lawesson's Reagent (66 g, 163.0 mmol) in toluene (1 L) was heated at 120° C. for 3 h. The reaction mixture was cooled to ambient temperature and the solvent was removed in vacuo. The residue was purified by column chromatography on silica gel (eluting with 3% EtOAc in petroleum ether) to give (R)-2-(6-nitro-3-thioxo-2,3-dihydro-benzo[1,4]oxazin-4-yl)-propionic acid ethyl ester (75.0 g, 89%) as a yellow solid. 1H NMR (CDCl3, 400 MHz): δ 8.06 (dd, J=2.4, 8.8 Hz, 1H), 7.87 (d, J=2.4 Hz, 1H), 7.21 (d, J=8.8 Hz, 1H), 6.71 (m, 1H), 5.06 (d, J=15.6 Hz, 2H), 4.32 (q, J=7.2 Hz, 2H), 1.76 (d, J=7.6 Hz, 3H), 1.28-1.21 (t, J=7.2 Hz, 3H). SFC (Table 2, Method 3) Rt=4.04 min.

Provenance & Evidence