C1(S([N:10]2[C:18]3[C:13](=[CH:14][C:15]([CH2:19][CH3:20])=[CH:16][CH:17]=3)[CH2:12][CH2:11]2)(=O)=O)C=CC=CC=1.[OH-].[Na+]>Br>[CH2:19]([C:15]1[CH:14]=[C:13]2[C:18](=[CH:17][CH:16]=1)[NH:10][CH2:11][CH2:12]2)[CH3:20]A mixture of 1-benzenesulfonyl-5-ethyl-2,3-dihydro-1H-indole (15 g, 0.05 mol) in HBr (48%, 162 mL) was heated at reflux for 6 h. The mixture was basified with sat. NaOH solution to pH 9 and extracted with ethyl acetate. The organic layer was washed with brine, dried over Na2SO4 and concentrated under reduced pressure. The residue was purified by column chromatography on silica gel to give 5-ethyl-2,3-dihydro-1H-indole (2.5 g, 32%).
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