[CH2:1]([O:8][C:9]1[CH:10]=[C:11]2[C:15](=[CH:16][CH:17]=1)[NH:14][CH:13]=[CH:12]2)[C:2]1[CH:7]=[CH:6][CH:5]=[CH:4][CH:3]=1.[BH3-]C#N.[Na+].O.[OH-].[K+]>C(O)(=O)C>[CH2:1]([O:8][C:9]1[CH:10]=[C:11]2[C:15](=[CH:16][CH:17]=1)[NH:14][CH2:13][CH2:12]2)[C:2]1[CH:3]=[CH:4][CH:5]=[CH:6][CH:7]=1In analogy to the method described by Gordon W. Gribble, Joseph H. Hoffmann Synthesis 1977, 859-860, the following reaction was performed. To a precooled solution of 22.3 g (0.1 mol) 5-benzyloxyindole in 270 ml acetic acid, 19 g (0.3 mol) NaCNBH3 were added. The solution was stirred at RT for 2 h, the volume was reduced to one third and poured into 300 ml water. KOH was added under cooling and the solution was extracted with ether. The combined organic phases were washed with water, dried over Na2SO4 and evaporated to yield 20.1 g (89%) 5-Benzyloxy-2,3-dihydro-1H-indole as colorless oil, MS: 225 (M).
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