[F:1][C:2]1[CH:9]=[CH:8][C:5]([CH2:6][NH2:7])=[CH:4][CH:3]=1.[F:10][C:11]([F:22])([F:21])[C:12]([N:14]1[CH2:19][CH2:18][C:17](=O)[CH2:16][CH2:15]1)=[O:13].C(O)(=O)C.[BH3-]C#N.[Na+]>CO>[F:1][C:2]1[CH:9]=[CH:8][C:5]([CH2:6][NH:7][CH:17]2[CH2:18][CH2:19][N:14]([C:12](=[O:13])[C:11]([F:10])([F:21])[F:22])[CH2:15][CH2:16]2)=[CH:4][CH:3]=1
4-Fluorobenzylamine (3.14 g, 25.9 mmol) was dissolved in methanol (150 mL). 1-(trifluoroacetyl)-4-piperidone (5.07 g, 25.9 mmol) was added and the pH was adjusted to ˜5 with acetic acid. The reaction mixture was stirred for 5 min and NaBH3CN (2.46 g, 38.9 mmol) was added slowly under stirring. After 20 h at room temperature the reaction was concentrated 2 M NaOH (100 mL) was added and the aqueous phase was extracted with dichloromethane (2×100 mL). The combined organic phases were dried over Na2SO4, filtered and concentrated to give N-(4-fluorobenzyl)-1-(trifluoroacetyl)piperidin-4-amine (50ELH85, 2.91 g, 37%).
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