[BH4-].[Na+].[C:3]1([S:9]([N:12]2[C:20]3[C:15](=[CH:16][C:17]([C:21](=O)[CH3:22])=[CH:18][CH:19]=3)[CH2:14][CH2:13]2)(=[O:11])=[O:10])[CH:8]=[CH:7][CH:6]=[CH:5][CH:4]=1.O.[OH-].[Na+]>C(O)(C(F)(F)F)=O>[CH2:21]([C:17]1[CH:16]=[C:15]2[C:20](=[CH:19][CH:18]=1)[N:12]([S:9]([C:3]1[CH:8]=[CH:7][CH:6]=[CH:5][CH:4]=1)(=[O:11])=[O:10])[CH2:13][CH2:14]2)[CH3:22]
To TFA (1600 mL) at 0° C. was added sodium borohydride (64.0 g, 1.69 mol) over 1 h. To this mixture was added dropwise a solution of 1-(1-(phenylsulfonyl)indolin-5-yl)ethanone (40.0 g, 0.133 mol) in TFA (700 mL) over 1 h. The mixture was then stirred overnight at 25° C. After dilution with H2O (1600 mL), the mixture was made basic by the addition of sodium hydroxide pellets at 0° C. The organic layer was separated and the aqueous layer was extracted with CH2Cl2. The combined organic layers were washed with brine, dried over Na2SO4 and concentrated under reduced pressure. The residue was purified by silica column to give 5-ethyl-1-(phenylsulfonyl)indoline (16.2 g, 47% over two steps).
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