The general procedure for the synthesis of 3-methyl-4-amino-5-bromopyridine from 3-methyl-4-aminopyridine is as follows:
Step 1: To a solution of 4-amino-3-methylpyridine (97, 10 g, 0.092 mol) and hydrobromic acid (HBr, 50 mL) heated to 70 °C was slowly added 15% hydrogen peroxide (H2O2, 16 mL) over a period of 1 hour. The reaction mixture was continued to be stirred at 70 °C for 1 h. The reaction was subsequently quenched by pouring into ice (100 g). The pH of the reaction mixture was adjusted to about 5 with 50% sodium hydroxide (NaOH) solution and the resulting red precipitate was collected by filtration. Subsequently, the pH of the filtrate was adjusted to about 9 and the resulting white precipitate was collected by filtration to afford 3-methyl-4-amino-5-bromopyridine (98, 13.5 g, 78% yield).
