[Li+].CC([N-]C(C)C)C.[Br:9][C:10]1[S:11][CH:12]=[CH:13][CH:14]=1.[F:15][C:16]1[CH:23]=[CH:22][C:19]([CH2:20]Br)=[CH:18][CH:17]=1.Cl>C1COCC1>[Br:9][C:10]1[S:11][C:12]([CH2:20][C:19]2[CH:22]=[CH:23][C:16]([F:15])=[CH:17][CH:18]=2)=[CH:13][CH:14]=1
To a -78° C. solution of LDA (19.3 mmol) in THF was added 2-bromothiophene (3.00 g, 18.4 mmol) and the reaction mixture was stirred for 15 min. A solution of 4-fluorobenzyl bromide (3.65 g, 19.3 mmol) in THF (1 mL) was added dropwise and the reaction mixture was warmed slowly to ambient temperature and stirred for 70 hours. The reaction mixture was poured into 0.5N aqueous HCl and extracted twice with ether. The combined organic layers were washed with saturated aqueous NaHCO3 (2×) and brine, dried over MgSO4, filtered, and concentrated in vacuo. Chromatography on silica gel (hexanes, then 3% ether/hexanes) gave 2-bromo-5-(4-fluorophenylmethyl)thiophene (2.25 g, 45%).
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