The general procedure for the synthesis of 2-bromoquinoline from 1-methyl-2-quinolone was as follows: Triphenylphosphine (1186 mg, 4.52 mmol) and dibromoisocyanuric acid (652 mg, 2.27 mmol) were sequentially added to a 50 mL round bottom flask fitted with a magnetic stirrer and a balloon (for pressure equilibrium) under nitrogen protection. The mixture was heated to 115 °C, at which point the dibromoisocyanuric acid reacted vigorously, and the reaction was continued to maintain this temperature for 10 min. Subsequently, 1-methylquinolin-2(1H)-one (239 mg, 1.50 mmol) was added to the reaction system and the temperature of the reaction was raised to 160-170°C for 16 hours. After completion of the reaction, the reaction mixture was dissolved in dichloromethane and alkalized with triethylamine. Purification was carried out by silica gel column chromatography with hexane-ethyl acetate (6:1, v/v) as eluent to finally obtain 2-bromoquinoline (244 mg, 78% yield). 2-bromoquinoline was a yellow oil, and its 1H-NMR (CDCl3) data were as follows: δ 7.51 (1H, d, J = 8.4 Hz), 7.51-8.20 (4H, m), 7.98 ( 1H, d, J = 8.4Hz).
