86847-84-9

68-12-2

127446-34-8

General procedure: synthesis of Intermediate 6: Intermediate 5 (19.28 g, 90.6 mmol) was dissolved in THF (181 mL), cooled to -20 °C, 77-BuLi (108.8 mL, 272 mmol) was slowly added, and the temperature was kept at -20 °C with stirring for 3 hours. Subsequently, DMF (20.81 mL, 271.86 mmol) was added dropwise to the reaction mixture and gradually warmed to room temperature. After completion of the reaction, the mixture was poured into pre-cooled 6N HCl and stirred for 15 min. It was neutralized with anhydrous K2CO3 to pH=7 and then extracted with Et2O. The organic layers were combined, washed sequentially with water and brine and dried over anhydrous Na2SO4. After concentration under reduced pressure, it was purified by recrystallization from a solvent mixture of EtOAc and hexane to afford N-(6-chloro-3-formylpyridin-2-yl)pivalamide (Intermediate 6) (12.84 g, 59% yield).