Synthesis
The general procedure for the synthesis of 2-methyl-3-bromo-5-aminopyridine from 5-bromo-6-methylnicotinic acid was as follows: 5-bromo-6-methylpyridine-3-carboxylic acid (1 g, 4.63 mmol) was dissolved in a solvent mixture of tert-butanol (6.6 mL) and N,N-dimethylformamide (15 mL), followed by triethylamine (5.15 mL, 37.04 mmol) and diphenylphosphoryl azide (0.51 mL, 5.093 mmol). The reaction mixture was heated to 100°C and stirred for 2 hours. Upon completion of the reaction, the progress was monitored by thin layer chromatography (TLC). The solvent was evaporated to dryness and the residue was dissolved in saturated sodium bicarbonate solution and extracted with ethyl acetate. The organic phase was dried over anhydrous sodium sulfate and filtered and the solvent was evaporated to dryness. The residue was purified by silica gel column chromatography to give a white solid. The white solid was dissolved in dichloromethane (10 mL), a dioxane solution of 4N HCl was added and stirred for 2 hours at room temperature. Upon completion of the reaction, the solvent was evaporated to dryness to give 5-bromo-6-methylpyridin-3-ylamine (white solid, 130 mg).
