[CH2:1]=[C:2]([O:5][Si](C)(C)C)[CH:3]=[CH2:4].[Br:10][C:11]1[CH:19]=[C:18]2[C:14]([CH2:15][C:16](=[CH2:21])[C:17]2=[O:20])=[CH:13][C:12]=1[F:22].B(F)(F)F.CCOCC>C(Cl)Cl>[Br:10][C:11]1[CH:19]=[C:18]2[C:14]([CH2:15][C:16]3([CH2:4][CH2:3][C:2](=[O:5])[CH2:1][CH2:21]3)[C:17]2=[O:20])=[CH:13][C:12]=1[F:22]To a cold (0° C.) solution of (buta-1,3-dien-2-yloxy)trimethylsilane (1.86 mL, 10.6 mmol) in DCM (80 mL) was 6-bromo-5-fluoro-2-methylene-2,3-dihydro-1H-inden-1-one (Intermediate 5, 2.32 g, 9.62 mmol) added. Boron trifluoride diethyl etherate (0.594 mL, 4.81 mmol) was added at 0° C. The reaction was stirred for 30 min., and then quenched with MeOH (1.0 mL). The reaction mixture was acidified with aq. 2 M HCl solution, and extracted with DCM. The organic phase was washed with brine, dried over sodium sulfate and concentrated. The product was purified by flash column chromatography using a stepwise gradient of heptane/EtOAc (7:1-3.5:1-1:1), to give the title compound (1.60 g, 53% yield). 1H NMR (500 MHz, CDCl3) δ ppm 1.83-1.94 (m, 2 H) 2.17-2.27 (m, 2 H) 2.38-2.51 (m, 2 H) 2.72 (dt, 2 H) 3.18 (s, 2 H) 7.25 (d, 1 H) 8.01 (d, 1 H); MS (ES+) m/z 311,313 [M+H]+.
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