Br[C:2]1[CH:11]=[CH:10][C:5]2[C:6](=[O:9])[O:7][CH2:8][C:4]=2[C:3]=1[F:12].[CH:13]([B-](F)(F)F)=[CH2:14].[K+]>CCO.C1C=CC(P(C2C=CC=CC=2)[C-]2C=CC=C2)=CC=1.C1C=CC(P(C2C=CC=CC=2)[C-]2C=CC=C2)=CC=1.Cl[Pd]Cl.[Fe+2]>[F:12][C:3]1[C:2]([CH:13]=[CH2:14])=[CH:11][CH:10]=[C:5]2[C:4]=1[CH2:8][O:7][C:6]2=[O:9]A mixture of 5-bromo-4-fluoro-2-benzofuran-1(3H)-one (5.0 g, 21.6 mmol), potassium vinyltrifluoroborate (4.4 g, 32.5 mmol) and Pd(dppf)Cl2 (500 mg) in 100 mL of TEA and 100 mL of EtOH was heated to reflux under N2 for 4 hrs and then concentrated. The resulting oil was purified by column chromatography to give 4-fluoro-5-vinyl-3H-isobenzofuran-1-one. 1H-NMR (400 MHz, CDCl3) δ ppm 7.67-7.68 (m, 2H), 6.90-6.97 (m, 1H), 6.00 (d, J=17.2 Hz, 1H), 5.60 (d, J=11.0 Hz, 1H), 5.35 (s, 2H).
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