Nitric Acid → 7-Fluoro-6-nitro-2H-1,4-benzoxazin-3(4H)-one

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Reaction Steps

To a stirred solution of the compound of Step B, Example 3, (48.9 gm, 292.8 mmol) and concentrated H2SO4 (100 mL), under N2, was added a 26 mL mixture of HNO3 (69-71%) and concentrated H2SO4 dropwise at 25°-35° C. (ice-bath). The resultant solution was stirred at room temperature for 10 minutes. 400 mL of ice water was added portionwise to the solution at 0° C. (ice-bath) followed by the addition of EtOAc (1.5 L). The organic layer was separated, dried (MgSO4) and evaporated to dryness to give the title compound of Step C as a tan solid (60.0 gm), 96%; m.p. 200°-202° C.; IR (nujol, cm-1): 1703.5 (C=O); 1H NMR δ: 4.79 (s,2H), 7.26-7.29 (d,1H), 7.63-7.64 (d,1H), 11.05 (s,1H).

Provenance & Evidence