C([BH3-])#N.[Na+].[C:5]([C:7]1[CH:14]=[CH:13][C:10]([CH:11]=O)=[CH:9][CH:8]=1)#[N:6].[NH:15]1[CH2:20][CH2:19][CH2:18][CH2:17][CH2:16]1.C(O)(=O)C>CO>[N:15]1([CH2:11][C:10]2[CH:13]=[CH:14][C:7]([C:5]#[N:6])=[CH:8][CH:9]=2)[CH2:20][CH2:19][CH2:18][CH2:17][CH2:16]1Under a nitrogen atmosphere, add sodium cyanoborohydride (5.77 g, 91.6 mmol) to a solution of 4-cyanobenzaldehyde (3 g, 22.9 mmol), piperidine (5.84 g, 68.7 mmol) and acetic acid (2.75 g, 45.8 mmol) in methanol (30 mL) at 0° C. with stirring. Warm the mixture to room temperature and stir overnight. Add water (100 mL), saturated aqueous K2CO3 (50 mL), and extract with DCM. Wash the combined organic extracts with water and brine. Dry the organic phase over Na2SO4, filter, and concentrate in vacuo. Purify by chromatography on silica gel (400 g) eluting with hexane/EtOAc (1:0 to 4:1 gradient) to obtain the desired intermediate as a clear oil (2.48 g, 54%). MS (APCI+) m/z: 201 (M+H)+.
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