1211540-92-9

407-20-5

1211540-92-9

General procedure for the synthesis of 3-fluoro-4-chloro-5-bromopyridine from 3-bromo-5-fluoropyridine: first, diisopropylamine (6.899 g, 9.555 mL, 68.18 mmol) was dissolved in THF (75 mL) and the solution was cooled to -78 °C. Subsequently, butyl lithium (25 mL, 2.5 M hexane solution, 62.5 mmol) was added to this solution. The reaction mixture was slowly warmed to -20 °C and then cooled again to -78 °C. At this temperature, a THF (25 mL) solution of 3-bromo-5-fluoropyridine (10 g, 56.82 mmol) was added dropwise, making sure that the temperature was always below -70 °C (the dropwise addition was completed in about 30 min). After completion of the dropwise addition, the reaction mixture was continued to be stirred at -78 °C for 30 min. Next, a solution of 1,1,1,2,2,2-hexachloroethane (14.8 g, 62.5 mmol) in THF (20 mL) was added slowly by dropwise addition, keeping the temperature below -70°C (about 30 minutes to complete the dropwise addition). After completion of the dropwise addition, the mixture was stirred at -78 °C for 20 min, after which it was allowed to warm slowly to room temperature, then cooled to 0 °C and the reaction was quenched with 100 mL of water. EtOAc (400 mL) was added for extraction and the organic layer was separated, washed sequentially with water (2 times) and brine (1 time), then dried over MgSO4, filtered and concentrated in vacuum to give a brown solid. This solid was ground in 100 mL of pentane for 10 min, filtered, and the filtrate was concentrated in vacuum to give a brown product, which was converted to a crystalline solid (11.85 g, 89% yield) after standing. The 1H NMR (DMSO-d6) data of the product was δ 8.78 (s, 1H), 8.76 (s, 1H). Next, 3-bromo-4-chloro-5-fluoropyridine (7.56 g, 32.18 mmol) was dissolved in 100 mL of pentane and hydrogen chloride (2M ethyl ether solution, 17.7 mL, 35.4 mmol) was added to produce an off-white precipitate immediately. After stirring for 5 min, the solid was collected by filtration, washed with pentane and dried by suction to give the target product as an off-white solid (4.79 g, 60% yield). The 1H NMR (DMSO-d6) data of the product were δ 8.77 (s, 1H), 8.75 (s, 1H).