Br[C:2](Br)=[CH:3][C:4]1[O:5][CH:6]=[CH:7][CH:8]=1.C([Li])CCC.Cl[C:16]1([C:28]([F:31])([F:30])[F:29])[C:21]2[CH:22]=[C:23]([Cl:26])[CH:24]=[CH:25][C:20]=2[NH:19][C:18](=[O:27])[O:17]1>C1COCC1>[Cl:26][C:23]1[CH:24]=[CH:25][C:20]2[NH:19][C:18](=[O:27])[O:17][C:16]([C:2]#[C:3][C:4]3[O:5][CH:6]=[CH:7][CH:8]=3)([C:28]([F:29])([F:30])[F:31])[C:21]=2[CH:22]=1To a solution of 5.9 g (25 mmoles) of 1,1-dibromo-2-(furan-2-yl)ethylene in 124 mL of anhydrous THF at -20° was added dropwise 31.0 mL of 1.6 M n-butyllithium in hexanes (50 mmoles). This solution was allowed to warm to ambient temperature over a period of 30 min, after which time it was cooled to -50°. 4,6-Dichloro-4-(trifluoromethyl)-2H-3,1-benzoxazin-2-one (2.65 g, 9.27 mmoles) was added in one portion, and the resulting solution was allowed to warm to -35° over 40 min. The reaction was quenched by the addition of aqueous ammonium chloride, and this mixture was poured onto water and extracted twice with ethyl acetate. The combined extracts were washed with brine, dried over sodium sulfate, and evaporated. The crude product was purified by column chromatography on silica gel (elution with 15% and 30% ethyl acetate in hexanes) affording 3.5 g of a solid which was recrystallized from ethyl acetate/hexanes to afford 3.03 g (95.7%) of the title compound.
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