Lawesson's reagent → 2-(7-Fluoro-6-nitro-3-thioxo-2,3-dihydro-benzo[1,4]oxazin-4-yl)-propionic acid ethyl ester

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Reaction Steps

A suspension of 2-(7-fluoro-6-nitro-3-oxo-2,3-dihydro-benzo[1,4]oxazin-4-yl)-propionic acid ethyl ester (1.170 g, 3.75 mmol) and Lawesson's reagent (1.516 g, 3.75 mmol) in toluene (40 mL) was heated at reflux for 3 h then cooled to ambient temperature. The reaction mixture was filtered and the filtrate was concentrated in vacuo. The residue was purified by column on silica gel (eluting with 0%˜10% EtOAc in petroleum ether) to give 2-(7-fluoro-6-nitro-3-thioxo-2,3-dihydro-benzo[1,4]oxazin-4-yl)-propionic acid ethyl ester as a light yellow solid (1.05 g, 85%). 1H NMR (DMSO-d6, 400 MHz): δ 7.86 (d, J=6.8 Hz, 1H), 7.43 (d, J=11.6 Hz, 1H), 6.16 (brs, 1H), 5.07 (s, 2H), 4.02-4.10 (q, J=7.2 Hz, 2H), 1.58 (d, J=6.8 Hz, 3H), 1.04 (t, J=7.2 Hz, 3H).

Provenance & Evidence