[O:1]1[CH2:5][CH2:4][CH2:3][CH2:2]1.[Br:6][C:7]1[S:8][C:9](Br)=[CH:10][CH:11]=1.[CH2:13]([Li])[CH2:14][CH2:15][CH3:16]>O>[Br:6][C:7]1[S:8][C:9]([CH:5]([C:4]2[CH:13]=[CH:14][C:15]([CH3:16])=[CH:2][CH:3]=2)[OH:1])=[CH:10][CH:11]=1To an anhydrous tetrahydrofuran (70.0 mL) solution of 2,5-dibromothiophene (5.00 g, 19.6 mmol) was added dropwise n-butyl lithium (2.55 M n-hexane solution, 7.69 mL, 19.6 mmol) on a dry ice-ethanol bath (−78° C.) under nitrogen atmosphere, which was stirred for 20 minutes at −78° C. p-Tolaldehyde (2.35 g, 19.6 mmol) was then added dropwise and stirred for 10 minutes at −78° C. The reaction mixture was allowed to room temperature and water was added, followed by extraction with ethyl acetate. The organic layer was washed with saturated aqueous sodium chloride, and the solvent was evaporated under a reduced pressure. The residue was purified by NH silica gel column chromatography (ethyl acetate:heptane=1:5→1:1) to obtain the title compound (4.30 g, 77.5%).
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