[NH2:1][C:2]1[CH:7]=[CH:6][C:5]([S:8]([C:11]2[CH:16]=[CH:15][CH:14]=[CH:13][CH:12]=2)(=[O:10])=[O:9])=[CH:4][C:3]=1[OH:17].C(=O)(O)[O-].[Na+].Cl[CH2:24][C:25](Cl)=[O:26].C(=O)([O-])[O-].[K+].[K+]>C(#N)C.O.CCOC(C)=O>[C:11]1([S:8]([C:5]2[CH:6]=[CH:7][C:2]3[NH:1][C:25](=[O:26])[CH2:24][O:17][C:3]=3[CH:4]=2)(=[O:10])=[O:9])[CH:16]=[CH:15][CH:14]=[CH:13][CH:12]=1A solution of 2-amino-5-benzenesulfonyl-phenol (0.392 g., 1.57 mmol) in 10 mL of acetonitrile was cooled to O° C. To this solution was added sodium bicarbonate (0.263 g., 3.14 mmol) in 4 mL water. With stirring, 2-chloroacetyl chloride (0.162 mL, 2.097 mmol) was added dropwise over 2 minutes. Stirring was continued for one hour as the reaction mix was warmed to room temperature. Potassium carbonate (0.261 g., 1.89 mmol) was then added and the system was warmed to reflux (85° C.) for two hours. The reaction mixture was added to 50 mL EtOAc, the aqueous fraction was separated and the organic layer was washed twice with 50 mL water, dried over Na2SO4 and concentrated in vacuo. The crude solid was recrystallized from a mixture of 30 mL each of ethanol and water to give 0.382 g (1.32 mmol, 84%) of 7-benzenesulfonyl-4H-benzo[1,4]oxazin-3-one as a yellow solid. MS: 288 (M−H)−. Step 6:
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