[CH3:1][S:2][C:3]1[CH:11]=[C:10]2[C:6]([CH:7]=[CH:8][NH:9]2)=[CH:5][CH:4]=1.[OH-].[Na+].[C:14]1([S:20](Cl)(=[O:22])=[O:21])[CH:19]=[CH:18][CH:17]=[CH:16][CH:15]=1>[N+](CCCC)(CCCC)(CCCC)CCCC.[O-]S(O)(=O)=O.ClCCl>[CH3:1][S:2][C:3]1[CH:11]=[C:10]2[C:6]([CH:7]=[CH:8][N:9]2[S:20]([C:14]2[CH:19]=[CH:18][CH:17]=[CH:16][CH:15]=2)(=[O:22])=[O:21])=[CH:5][CH:4]=1To a solution of 6-(methylthio)-1H-indole (1 g, 6.13 mmol), NaOH (4.90 g, 122.6 mmol) and Bu4NHSO4 (207.8 mg, 0.613 mmol) in dichloromethane (20 mL) was added benzenesulfonyl chloride (1.29 g, 7.36 mmol). The reaction mixture was stirred at rt overnight. The mixture was quenched with water (30 mL) and extracted with CH2Cl2 (30 mL×3). The combined organic layers were dried over anhydrous Na2SO4, filtered, concentrated and purified by column chromatography on silica gel eluted with (petroleum ether/EtOAc 10:1) to afford 6-(methylthio)-1-(phenylsulfonyl)-1H-indole (1.1 g, 59.18% yield) as a white solid. LC-MS MS (ESI) m/z 304.0 [M+H]+. 1H NMR (CDCl3 400 MHz): δ 7.93-7.75 (m, 3H), 7.58-7.41 (m, 5H), 7.17 (dd, J1=8.0 Hz, J2=1.6 Hz, 1H), 6.63-6.60 (m, 1H), 2.53 (s, 3H).
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