Trifluoroacetic anhydride → 2-(6-Acetoxy-3-oxo-2,3-dihydro-benzo[1,4]oxazin-4-yl)-propionic acid ethyl ester

Participants

Reaction Steps

To a suspension of urea-hydrogen peroxide (5.93 g, 63 mmol) and NaHCO3 (5.93 g, 63 mmol) in DCM (60 mL) at 0° C. was added 2-(6-acetyl-3-oxo-2,3-dihydro-benzo[1,4]oxazin-4-yl)-propionic acid ethyl ester (6.14 g, 21 mmol). The reaction mixture was stirred for 10 min and TFAA (5.84 mL, 42 mmol) was added dropwise. The reaction mixture was stirred at 0° C. for 1 h and then 3 days at ambient temperature. The reaction mixture was diluted with DCM (60 mL), quenched with saturated Na2S2O3 solution (30 mL) and washed with water (30 mL). The combined organic phase was dried over anhydrous Na2SO4, filtered and concentrated in vacuo to give 2-(6-acetoxy-3-oxo-2,3-dihydro-benzo[1,4]oxazin-4-yl)-propionic acid ethyl ester, which was used in the next step directly without purification. TLC (eluting with 25% EtOAc/heptane) Rf=0.4.

Provenance & Evidence