[F:1][C:2]1[C:19]([F:20])=[CH:18][C:5]([C:6]([NH:8][C:9]2[CH:14]=[CH:13][C:12]([N+:15]([O-:17])=[O:16])=[CH:11][CH:10]=2)=[O:7])=[C:4]([OH:21])[CH:3]=1.[C:22]1(C)C=CC(S(O)(=O)=O)=CC=1.O.C(=O)(O)[O-].[Na+]>C1(C)C=CC=CC=1>[F:20][C:19]1[C:2]([F:1])=[CH:3][C:4]2[O:21][CH2:22][N:8]([C:9]3[CH:14]=[CH:13][C:12]([N+:15]([O-:17])=[O:16])=[CH:11][CH:10]=3)[C:6](=[O:7])[C:5]=2[CH:18]=1
To 4,5-difluoro-2-hydroxy-N-(4-nitrophenyl)benzamide (0.13 g, 0.44 mmol) in toluene (5 ml) was added paraformadehyde (0.3 g, 10 mmol) and p-toluenesulfonic acid (0.01 g, 0.05 mmol) and the reaction heated to 120° C. for 3 hr with azeotropic removal of water. Saturated sodium bicarbonate (10 ml) was added and product extracted with ethyl acetate, dried over anhydrous sodium sulfate and concentrated to give 0.11 mg (81%) of 6,7-difluoro-3-(4-nitrophenyl)-2,3-dihydrobenzo[e][1,3]oxazin-4-one. RP-HPLC: 2.54 min; ES-MS (M+H)+=307.0; 1H-NMR (MeOH-d4) δ (ppm): 5.78 (s, 2 H), 7.04 (dd, 1 H), 7.64 (d, 2 H), 7.82 (dd, 1 H), 8.3 (d, 2 H).
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