The reaction system was cooled to -78 °C under an inert atmosphere and bromoacetyl bromide (53.7 mmol, 1 eq.) was added slowly and dropwise to a solution of N-BOC-piperazine (53.7 mmol, 1 eq.) and triethylamine (59.1 mmol, 1.1 eq.) dissolved in dichloromethane (150 mL). The reaction mixture was stirred continuously at -78 °C for 3 h. The reaction mixture was subsequently diluted with dichloromethane (75 mL) and washed with deionized water. The organic layer was separated, dried over anhydrous magnesium sulfate and concentrated under reduced pressure to remove the solvent. The crude product was recrystallized with ether, filtered and dried in vacuum to give tert-butyl 4-(2-bromoacetyl)piperazine-1-carboxylate (6q). The product was a white solid with 78% yield and melting point 23-242°C. The product was a white solid with a melting point of 23-242°C. The product was a white solid with 78% yield. Molecular weight: 307.18 g/mol. IR spectrum (KBr, cm?1): 2965(m), 1689(s), 1632(s), 1417(s), 1246(s), 1167(s), 1023(m). NMR hydrogen spectrum (250 MHz, CDCl?) δ: 3.87 (s, 2H), 3.61-3.57 (m, 2H), 3.55-3.47 (m, 4H), 3.46-3.41 (m, 2H), 1.46 (s, 9H). NMR carbon spectrum (63 MHz, CDCl?) δ: 165.5 (Cq), 154.5 (Cq), 80.5 (Cq), 46.6 (2CH?), 40.9 (2CH?), 28.4 (3CH?), 25.7 (CH?).
