Acetic Anhydride → 2-methyl-5-nitro-4H-benzo[d][1,3]oxazin-4-one

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Reaction Conditions

Reaction Steps

A mixture of 2-amino-6-nitro-benzoic acid (1.5 g, 8.2 mmol) in acetic anhydride (15 mL) was heated at 200° C. for 30 minutes in a microwave oven. The mixture was filtered and washed with ethyl acetate (20 mL). The filtrate was concentrated in vacuo. The solid was stirred in ether (20 mL) for 2 hrs. The suspension was filtered and washed with ether (20 mL) to give 2-methyl-5-nitro-benzo[d][1,3]oxazin-4-one as a light brown solid (1.4 g, 85% yield): HPLC: Waters Symmetry C18, 5 μm, 3.9×150 mm, 1 mL/min, 240 nm, CH3CN/0.1% H3PO4, 5% grad 95% in 5 min, 5.36 min (92%); 1H NMR (DMSO-d6) δ 2.42 (s, 3H, CH3), 7.79 (dd, J=1, 8 Hz, 1H, Ar), 7.93 (dd, J=1, 8 Hz, 1H, Ar), 8.06 (t, J=8 Hz, 1H, Ar); 13C NMR (DMSO-d6) δ 20.87, 107.79, 121.54, 128.87, 137.19, 147.12, 148.46, 155.18, 161.78; LCMS: MH=207.

Provenance & Evidence