[Br:1][C:2]1[CH:9]=[CH:8][C:5]([CH:6]=O)=[C:4]([CH3:10])[CH:3]=1.[N:11]1([C:17]([O:19][C:20]([CH3:23])([CH3:22])[CH3:21])=[O:18])[CH2:16][CH2:15][NH:14][CH2:13][CH2:12]1.C(N(CC)CC)C.C(O[BH-](OC(=O)C)OC(=O)C)(=O)C.[Na+]>ClC(Cl)C>[Br:1][C:2]1[CH:9]=[CH:8][C:5]([CH2:6][N:14]2[CH2:13][CH2:12][N:11]([C:17]([O:19][C:20]([CH3:23])([CH3:22])[CH3:21])=[O:18])[CH2:16][CH2:15]2)=[C:4]([CH3:10])[CH:3]=1A 500 mL round-bottom flask was charged with 4-bromo-2-methylbenzaldehyde (8.00 g, 40.2 mmol, 1.00 equiv), tert-butyl piperazine-1-carboxylate (9.40 g, 50.5 mmol, 1.26 equiv), triethylamine (6.50 g, 64.2 mmol, 1.60 equiv) and dichloroethane (200 mL). The resulting solution was stirred for 30 min at room temperature. Solid sodium triacetoxyborohydride (27.0 g, 127 mmol, 3.17 equiv) was added. The resulting solution was stirred overnight at room temperature. The reaction progress was monitored by LCMS. The reaction was then quenched by the addition of water (100 mL). The resulting solution was extracted with dichloromethane (3×200 mL) and the organic layers were combined, washed with brine (2×200 mL), dried over anhydrous sodium sulfate and concentrated under reduced pressure. The residue was chromatographed on a silica gel column with ethyl acetate/petroleum ether (2/3) to yield 10.0 g (67% yield) of tert-butyl 4-[(4-bromo-2-methylphenyl)methyl]piperazine-1-carboxylate as a white solid. LCMS (ESI, m/z): 369 [M+H]+.
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