[Br:1][C:2]1[CH:3]=[C:4]([NH2:18])[C:5]([NH2:17])=[CH:6][C:7]=1[O:8][C:9]1[CH:14]=[CH:13][C:12]([F:15])=[CH:11][C:10]=1[F:16].[CH:19]([O-])([O-])OCC.O.C1(C)C=CC(S(O)(=O)=O)=CC=1>O1CCCC1>[Br:1][C:2]1[C:7]([O:8][C:9]2[CH:14]=[CH:13][C:12]([F:15])=[CH:11][C:10]=2[F:16])=[CH:6][C:5]2[N:17]=[CH:19][NH:18][C:4]=2[CH:3]=1A solution of 4-bromo-5-(2,4-difluorophenoxy)benzene-1,2-diamine (0.090 g, 0.28 mmol) in tetrahydrofuran (1.1 mL) was treated with ethyl orthoformate (0.142 mL, 0.857 mmol) followed by p-toluenesulfonic acid monohydrate (0.005 g, 0.03 mmol) and stirred at 50° C. for 1 h. The reaction mixture was concentrated and diluted with ethyl acetate and saturated sodium bicarbonate. The organic layer was separated and washed with brine, dried with magnesium sulfate, filtered, and concentrated to give a crude oil. Purification by flash column chromatography (100% hexanes to 100% EtOAc) gave the desired product (69 mg, 74%). LCMS calculated for C13H8BrF2N2O (M+H)+: m/z=325.0, 327.0. found: 325.0, 327.0.
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