Synthesis
6-Chloro-pyridin-3-ylamine was dissolved slowly with constant stirring in 48% HBr solution (50 mL) at r.t. and then the solution was cooled to -10 °C. A solution of sodium nitrite in cold water was added dropwise at -10 °C with constant stirring over 2 h, followed by a solution of copper (I) bromide in 48% HBr dropwise. The mixture was then stirred at r.t. until complete. The mixture was neutralized with sodium carbonate and extracted with ethyl acetate. The organic phase was washed with brine, dried over sodium sulfate, and concentrated. The residue was purified by column chromatography on silica gel (60-120 mesh) eluting with 1% ethyl acetate/petroleum ether to afford 5- bromo-2-chloropyridine.
