General procedure for the synthesis of 5-amino-2-bromo-6-iodopyridine from 5-amino-2-bromopyridine: To a stirring solution of 6-bromo-pyridin-3-ylamine (10.2 g, 0.0580 mol) and Ag2SO4 (18.1 g, 0.0580 mol) in ethanol (150 mL) was added iodine (7.59 g, 0.0580 mol). The reaction mixture was stirred overnight. Subsequently, hexane (200 mL) was added and the mixture was filtered through diatomaceous earth. The solvent was removed under reduced pressure and the residue was dissolved in chloroform (200 mL), washed sequentially with saturated aqueous sodium thiosulfate (100 mL) and water (1 x 100 mL), and dried over anhydrous sodium sulfate. The solvent was concentrated under reduced pressure and the residue was dissolved in hot ethyl acetate (100 mL), filtered and treated with hexane (100 mL). Filtration afforded a white crystalline product 5-amino-2-bromo-6-iodopyridine 11.2 g in 65% yield. 1H-NMR (CDCl3; 400 MHz): δ 7.10 (d, 1H, J=8.2 Hz), 6.74 (d, 1H, J=8.2 Hz), 4.06 (br s, 2H).
