[NH2:1][C:2]1[CH:7]=[C:6]([O:8][C:9]([F:12])([F:11])[F:10])[CH:5]=[CH:4][C:3]=1[OH:13].C1N=CN([C:19](N2C=NC=C2)=[O:20])C=1>O1CCOCC1>[F:12][C:9]([F:10])([F:11])[O:8][C:6]1[CH:5]=[CH:4][C:3]2[O:13][C:19](=[O:20])[NH:1][C:2]=2[CH:7]=1To a mixture of 2-amino-4-(trifluoromethoxy)phenol (1.01 g) and 1,4-dioxane (20 mL) was added CDI (1.10 g), followed by heating and stirring at 70° C. for 7 hours. The reaction mixture was cooled to room temperature, and then the solvent was concentrated to a half of the volume under reduced pressure. To the obtained residue was added water (30 mL), followed by adjusting to pH 4 by the addition of concentrated hydrochloric acid under ice-cooling, and stirring at the same temperature for 1 hour. The resulting solid was collected by filtration to obtain 5-(trifluoromethoxy)-1,3-benzoxazol-2(3H)-one (830 mg).
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