[Br:1][C:2]1[CH:3]=[CH:4][C:5]([CH:9]=O)=[N:6][C:7]=1[CH3:8].[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.ClCCCl.C(O[BH-](OC(=O)C)OC(=O)C)(=O)C.[Na+]>O>[Br:1][C:2]1[CH:3]=[CH:4][C:5]([CH2:9][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)=[N:6][C:7]=1[CH3:8]
A 250 mL round-bottom flask was charged with 5-bromo-6-methylpyridine-2-carbaldehyde (4.90 g, 24.6 mmol, 1.00 equiv), tert-butyl piperazine-1-carboxylate (4.60 g, 24.7 mmol, 1.01 equiv), 1,2-dichloroethane (150 mL). The resulting solution was stirred for 30 min at room temperature. Sodium triacetoxyborohydride (15.6 g, 73.6 mmol, 3.00 equiv) was added. The resulting solution was stirred overnight at room temperature and diluted with water (50 mL), extracted with dichloromethane (2×100 mL). The organic layers were combined, dried over anhydrous sodium sulfate, filtered and concentrated under reduced pressure. The residue was chromatographed on a silica gel column with ethyl acetate/petroleum ether (30/70) to provide 7.80 g (82% yield) of tert-butyl 4[(5-bromo-6-methylpyridin-2-yl)methyl]piperazine-1-carboxylate as a light yellow solid. LCMS (ESI, m/z): 370 [M+H]+.
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