[K].[Br:2][C:3]1[CH:4]=[CH:5][C:6]([F:14])=[C:7]([C:9]([CH:11]2[CH2:13][CH2:12]2)=O)[CH:8]=1.[C:15]1(C)C=CC=CC=1>[Br-].C[P+](C1C=CC=CC=1)(C1C=CC=CC=1)C1C=CC=CC=1>[Br:2][C:3]1[CH:4]=[CH:5][C:6]([F:14])=[C:7]([C:9]([CH:11]2[CH2:13][CH2:12]2)=[CH2:15])[CH:8]=1A suspension of methyltriphenylphosphonium bromide (7.142 g, 20 mmol) in toluene (50 ml) was treated with potassium amylate (1.7 M in toluene, 11.76 ml, 20 mmol), and the mixture was stirred at 0° C. for 30 minutes. A solution of (5-bromo-2-fluoro-phenyl)-cyclopropyl-methanone (4.05 g, 17 mmol) in toluene (17 ml) was added and the mixture stirred at room temperature for 2 hours. For the workup, the mixture was extracted with water and ethyl acetate, the organic layer separated, dried and evaporated at reduced pressure. After chromatography on silica gel using a mixture of hexane and ethyl acetate as the eluent, the 4-bromo-2-(1-cyclopropyl-vinyl)-1-fluoro-benzene was obtained as yellow oil (3.816 g, 95% of theory). Mass (calculated) C11H10BrF [241.102]; (found) [M+H]+=241, [M+2-H]+=243.
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