[NH2:1][C:2]1[CH:7]=[CH:6][CH:5]=[CH:4][C:3]=1[OH:8].C(=O)([O-])O.[Na+].Br[C:15]1[CH:20]=[C:19]([Cl:21])[CH:18]=[CH:17][C:16]=1[CH2:22][C:23](Cl)=[O:24]>C(OCC)(=O)C.O.C1(C)C=CC=CC=1>[Cl:21][C:19]1[CH:20]=[CH:15][C:16]([CH:22]2[C:23](=[O:24])[NH:1][C:2]3[CH:7]=[CH:6][CH:5]=[CH:4][C:3]=3[O:8]2)=[CH:17][CH:18]=1To a solution of 2-aminophenol (13.5 g) in ethyl acetate (150 ml) is added a solution of sodium hydrogen carbonate (15 g) in water (300 ml), and to the mixture is added dropwise a solution of o-bromo-4-chlorophenylacetyl chloride (32.2 g) in toluene with vigorous stirring under ice cooling. After the mixture is stirred at room temperature for one hour, the solvent in the organic layer is distilled off and the residue is dissolved in acetone. To the solution is added potassium carbonate (20 g), and the mixture is stirred at room temperature overnight. The solvent is distilled off and to the residue is added water. The mixture is extracted with ethyl acetate. The ethyl acetate layer is washed, dried and distilled to remove the solvent, and the residue is recrystallized from ethyl acetate-n-hexane to give 2-(4-chlorophenyl)-3-oxo-3,4-dihyro-2H-1,4-benzoxazine (24.0 g) as crystals. M.p. 180.5°-181.5° C.
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