GENERAL METHOD: To a solution of 2,6-dichloro-3-bromopyridine (4.70 g, 20.7 mmol) in dimethyl sulfoxide (DMSO, 103 mL) was added cesium fluoride (12.6 g, 82.9 mmol) at room temperature. The reaction mixture was stirred in air at 80 °C for 8 hours. After completion of the reaction, the mixture was poured into room temperature water and extracted with ether (Et2O). The organic layer was separated, washed sequentially with water and saturated saline, dried over anhydrous sodium sulfate (Na2SO4) and subsequently concentrated under reduced pressure (400 Torr, 40°C). Purification of the residue by column chromatography (silica gel, hexane solution of ethyl acetate as eluent) afforded 3-bromo-2,6-difluoropyridine (2.58 g, 64% yield) as a colorless oil.1H NMR (CDCl3) δ: 6.79 (1H, dd, J = 8.3, 3.0 Hz), 8.03 (1H, ddd, J = 8.4, 8.4, 7.0 Hz).19F NMR (CDCl3) δ: -69.3 Hz, -63.8 Hz.Compounds 4B-8B were prepared according to the method similar to 3B.
