[N:1]1([C:7]([O:9][C:10]([CH3:13])([CH3:12])[CH3:11])=[O:8])[CH2:6][CH2:5][NH:4][CH2:3][CH2:2]1.[Br:14][C:15]1[CH:22]=[CH:21][C:18]([CH:19]=O)=[C:17]([CH3:23])[CH:16]=1.C(N(CC)CC)C.C(O[BH-](OC(=O)C)OC(=O)C)(=O)C.[Na+]>O.ClCCl>[Br:14][C:15]1[CH:22]=[CH:21][C:18]([CH2:19][N:4]2[CH2:5][CH2:6][N:1]([C:7]([O:9][C:10]([CH3:13])([CH3:12])[CH3:11])=[O:8])[CH2:2][CH2:3]2)=[C:17]([CH3:23])[CH:16]=1A 250 mL round-bottom flask was charged with tert-butyl piperazine-1-carboxylate (2.80 g, 15.0 mmol, 1.00 equiv), 4-bromo-2-methylbenzaldehyde (3.28 g, 16.5 mmol, 1.10 equiv), dichloromethane (80 mL). Triethylamine (4.56 g, 45.1 mmol, 3.00 equiv) was added. The resulting solution was stirred for 30 mins at room temperature. Sodium triacetoxyborohydride (9.60 g, 45.3 mmol, 3.00 equiv) was added. The resulting solution was stirred overnight at room temperature and then diluted with water (100 mL). The resulting solution was extracted with dichloromethane (3×60 mL) and the organic layers were combined, dried over Na2SO4, filtered and concentrated under reduced pressure. The residue was chromatographed on a silica gel column with ethyl acetate/petroleum ether (20/80) to provide 5.70 g (98% yield) of tert-butyl 4-[(4-bromo-2-methylphenyl)methyl]piperazine-1-carboxylate as light yellow oil. LCMS (ESI, m/z): 369 [M+H]+.
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