Step d: Synthesis of 6-chloro-4-methylpyridin-2-amine; N-(6-chloro-4-methylpyridin-2-yl) neopentanamide (500 mg, 2.21 mmol) was dissolved in 6M hydrochloric acid solution (40 mL) and the reaction was stirred at 90 °C for 6 h. The reaction was carried out at 90 °C for 2 h. The reaction was carried out at 90 °C for 1 h. The reaction was carried out at 90 °C for 2 h. The reaction was carried out at 90 °C for 2 h. The reaction was carried out at 90 °C for 2 h. The reaction was carried out at 90 °C for 2 h. The reaction was carried out at 90 °C for 2 h. Upon completion of the reaction, the mixture was cooled to room temperature and neutralized with sodium hydroxide solution to pH 10. Subsequently, the mixture was extracted with ethyl acetate, the organic phases were combined and concentrated under reduced pressure. The crude product was purified by silica gel column chromatography with the eluent being a mixed solution of petroleum ether and ethyl acetate (95:5, v/v) to afford 6-chloro-4-methylpyridin-2-amine (257 mg, 82% yield). The product was characterized by 1H NMR (CDCl3, 300 MHz): δ 6.52 (s, 1H), 6.26 (s, 1H), 2.23 (s, 3H).
