[H-].[K+].Br[C:4]1[CH:12]=[C:11]2[C:7]([CH:8]=[CH:9][NH:10]2)=[CH:6][CH:5]=1.C([Li])(C)(C)C.[CH3:18][S:19]SC>O1CCCC1.[Cl-].[NH4+]>[CH3:18][S:19][C:4]1[CH:12]=[C:11]2[C:7]([CH:8]=[CH:9][NH:10]2)=[CH:6][CH:5]=1
To a stirred suspension of potassium hydride (30% dispersion in mineral oil, 0.68 g, 5.10 mmol) in dry tetrahydrofuran (20 mL) at 0° C., under Ar, was added a solution of 6-bromoindole (1.0 g, 5.1 mmol) in tetrahydrofuran (10 mL). After 15 mins, the solution was cooled to −78° C. and tert-butyllithium (1.7 M, 6.0 mL, 10 mmol) was added dropwise. The mixture was stirred for a further 15 mins and then dimethyl disulphide (0.92 mL, 10.2 mmol) was added dropwise. The solution was warmned gradually to room temperature, then diluted carefully with saturated ammonium chloride solution (20 mL). The mixture was extracted with ether (2×50 mL). The combined organic extracts were dried (magnesium sulfate), concentrated in vacuo and purified by column chromatography [SiO2; heptane-dichloromethane (1:1)] to give the product as a pale-yellow solid (0.56 g, 68%): mp. 91-92° C.; NMR δH (400 MHz, CDCl3) 2.51 (3H, s), 6.49 (1H, m), 7.09-7.16 (2H, m), 7.35 (1H, s), 7.54 (1H, d, J 8.2 Hz) and 8.09 (1H, br s); IR (Nujol)νmax/cm−1 3388, 2925, 1459, 1311, 1098, 810, 717 and 527.
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