c) Synthesis of 2,6-dibromopyridin-4-amine: iron powder (1.26 g, 22.56 mmol) was slowly added to a stirring solution of 2,6-dibromo-4-nitropyridine 1-oxide (Preparation 22b, 1.68 g, 5.64 mmol) in acetic acid (16 mL) at 0 °C. The reaction mixture was stirred continuously for 1 hour at room temperature. Upon completion of the reaction, water and ethyl acetate were added to the mixture for extraction. The organic layer was separated and washed sequentially with water, saturated aqueous potassium carbonate solution and brine, followed by drying with anhydrous magnesium sulfate. The solvent was evaporated under reduced pressure to give 2,6-dibromo-4-aminopyridine as a white solid (1.35 g, 96% yield).LRMS (m/z): 251/253/255 (M + 1)+.1H NMR (400 MHz, chloroform-d) δ ppm 4.33 (br.s., 2H), 6.68 (s, 2H).
