Step 1: Synthesis of tert-butyl 2-bromopyridin-3-ylcarbamate (10a)
To a solution of 2-bromopyridin-3-amine (3.0 g, 17.3 mmol) in tetrahydrofuran (THF, 30 mL) was slowly added lithium bis(trimethylsilyl)carbamate (1M, 35 mL, 35 mmol) at 0 °C. The reaction mixture was stirred at this temperature for 30 minutes. Subsequently, a solution of di-tert-butyl dicarbonate (Boc2O, 3.9 g, 17.3 mmol) in THF (20 mL) was added and the mixture was stirred at room temperature for 1.5 hours. Upon completion of the reaction, the reaction mixture was poured into 0.1 M hydrochloric acid (HCl) and extracted with ethyl acetate (EA). The organic layers were combined, washed with saturated saline (brine), dried over anhydrous sodium sulfate and concentrated under reduced pressure. The crude product was purified by column chromatography (CC, petroleum ether/ethyl acetate = 5/1) to afford the target compound 10a (2.9 g, 62% yield) as a white solid.
