[Li]CCCC.[F:6][C:7]1[CH:16]=[CH:15][C:10]2[S:11][CH:12]=[C:13]([CH3:14])[C:9]=2[CH:8]=1.[Cl:17][CH2:18][CH2:19][CH2:20]I.[NH4+].[Cl-]>C1COCC1.[Cu]I>[Cl:17][CH2:18][CH2:19][CH2:20][C:12]1[S:11][C:10]2[CH:15]=[CH:16][C:7]([F:6])=[CH:8][C:9]=2[C:13]=1[CH3:14]
n-BuLi in heptanes (1.5 ml, 2.4 mmol, 1.6M) was added drop wise to 5-fluoro-3-methyl-benzo[b]thiophene (332 mg, 2.0 mmol) in THF (5 ml) at −20° C. under argon. The reaction mixture was stirred at −15° C. for 30 min, then 1-chloro-3-iodopropane (322 μl, 3.0 mmol) and copper (1) iodide (38 mg, 0.2 mmol) were added. The reaction was stirred at −15° C. for 1 h, then NH4Cl (sat'd aq., 5 ml) was added. The product was extracted with diethyl ether (2×30 ml) and the organic layer was washed with brine (10 ml), dried (K2CO3), filtered and concentrated in vacuo. The product was purified by column chromatography (0–1% diethyl ether in heptanes) to give 2-(3-chloro-propyl)-5-fluoro-3-methyl-benzo[b]thiophene (180 mg, 37%). 1H NMR (CDCl3): δ 2.19 (tt, 2H), 2.22 (s, 3H), 2.94 (t, 2H), 3.57 (t, 2H), 7.04 (dt, 1H), 7.28 (dd, 1H), 7.66 (dd, 1H).
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