General procedure for the synthesis of N-BOC-3-bromopyrrolidine from (RS)-1-tert-butoxycarbonyl-3-hydroxypyrrolidine: (RS)-1-tert-butoxycarbonyl-3-hydroxypyrrolidine (3.00 g) was dissolved in THF (90 mL), and triphenylphosphine (12.4 g) and carbon tetrabromide (15.7 g) were added sequentially. Subsequently, THF (90 mL) was added slowly dropwise and the reaction mixture was stirred at room temperature overnight. Upon completion of the reaction, the organic solvent was removed by rotary evaporation. The residue was extracted with ethyl acetate (4 x 50 mL), and the combined organic phases were washed with deionized water, dried over anhydrous sodium sulfate, and rotary evaporated again to dryness. Finally, the residue was purified by fast column chromatography (silica gel, cyclohexane/ethyl acetate 80/20) to afford the target product, (RS)-1-tert-butoxycarbonyl-3-bromopyrrolidine, in 80% yield as a yellow oil.1H-NMR (300 MHz, DMSO-d6, δ ppm relative to TMS): δ 4.85 (1H, m) 3.70-3.59 (1H, m), 3.55-2.10 (5H, m), 1.35 (9H, s).
