Bromine → 5-Bromo-4-propylpyridine-2-amine

To a solution of 4-propylpyridin-2-amine (5.70 g, 41.8 mmol) in ethanol (210 mL), a solution of bromine in ethanol (bromine 2.38 mL/ethanol 50 mL) was added under ice-cold conditions, and the mixture was stirred under ice-cold conditions for 0.5 hours. Under ice-cold conditions, the reaction solution was added an aqueous solution of sodium hydrogen carbonate, concentrated in vacuo, and extracted with ethyl acetate. The organic layer was washed with brine, dried over anhydrous sodium sulfate, and concentrated in vacuo. The obtained residue was purified by silica-gel column chromatography (hexane/ethyl acetate), and the title compound (4.34 g (yield 48%)) was obtained as a brown oil.