[N+:1]([C:4]1[CH:5]=[C:6]2[C:10](=[CH:11][CH:12]=1)[NH:9][CH:8]=[CH:7]2)([O-:3])=[O:2].[OH-].[K+].[C:15]1([S:21](Cl)(=[O:23])=[O:22])[CH:20]=[CH:19][CH:18]=[CH:17][CH:16]=1>S(=O)(=O)(O)[O-].C([N+](CCCC)(CCCC)CCCC)CCC.C(Cl)Cl>[C:15]1([S:21]([N:9]2[C:10]3[C:6](=[CH:5][C:4]([N+:1]([O-:3])=[O:2])=[CH:12][CH:11]=3)[CH:7]=[CH:8]2)(=[O:23])=[O:22])[CH:20]=[CH:19][CH:18]=[CH:17][CH:16]=1
After a suspension of 5-nitroindole (25) (1.00 g, 6.17 mmol), tetrabutylammonium bisulfate (0.32 g, 0.93 mmol) and KOH (0.69 g, 12.33 mmol) in CH2Cl2 (20 mL) was stirred for 30 min, benzenesulfonyl chloride (1.18 ml, 9.25 mmol) was added and stirred at room temperature overnight. The reaction was quenched with water extracted with CH2Cl2 (20 mL×3). The combined organic layer was dried over anhydrous MgSO4 and concentrated under reduced pressure to give a yellow residue, which was purified by silica gel chromatography (EtOAc:n-hexane=1:4) to afford 26 (1.72 g). 1H NMR (500 MHz, CD3OD): δ 6.81 (d, J=3.6 Hz, 1H), 7.48-7.51 (m, 2H), 7.58-7.61 (m, 1H), 7.73 (d, J=3.69 Hz, 1H), 7.90 (d, J=7.64 Hz, 2H), 8.09 (d, J=9.0 Hz, 1H), 8.21 (dd, J=9.0, 2.0 Hz, 1H), 8.47 (d, J=2.0 Hz, 1H).
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