[S:1]1[C:5]([CH:6]=O)=[CH:4][C:3]2[CH:8]=[CH:9][CH:10]=[CH:11][C:2]1=2.[C:12](Br)(Br)([Br:14])[Br:13].C1(P(C2C=CC=CC=2)C2C=CC=CC=2)C=CC=CC=1>C(Cl)Cl>[Br:13][C:12]([Br:14])=[CH:6][C:5]1[S:1][C:2]2[CH:11]=[CH:10][CH:9]=[CH:8][C:3]=2[CH:4]=1A solution of benzo[b]thiophene-2-carbaldehyde (1.0 g, 6.17 mmol) and carbon tetrabromide (3.1 g, 9.25 mmol) in methylene chloride (50 mL) was cooled to 0° C. A solution of triphenylphosphine (4.86 g, 18.3 mmol) in methylene chloride (20 mL) was added dropwise. After ½ hour the solution was placed on a plug of silica gel and eluted with 20% ethyl acetate:hexane. Concentration of the eluent resulted in the isolation of 1.3 g (67%) of 2-(2,2-Dibromo-vinyl)-benzo[b]thiophene as a yellow oil, which was used as such in the next step.
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