Synthesis
A solution was prepared by dissolving 32.7 g (0.15 mol) di-tert-butyl dicarbonate (Boc anhydride) in 100 mL of tetrahydrofuran (THF) under nitrogen protection. This solution was slowly added dropwise to a reaction system containing 17.4 g (0.14 mol) of 2-amino-6-chloropyridine and 300 mL (0.30 mol) of 1 M sodium hexamethyldisilazide in THF (in 200 mL of THF). The reaction mixture was stirred overnight at room temperature. Upon completion of the reaction, the solvent was removed by rotary evaporation. The residue was partitioned between ethyl acetate (EtOAc) and 1 N aqueous hydrochloric acid solution, and the organic phase was separated after thorough stirring. The aqueous phase was extracted once more with EtOAc. All organic phases were combined and washed with 300 mL of saturated sodium bicarbonate solution, subsequently dried over anhydrous sodium sulfate, filtered and concentrated. The crude product was purified by recrystallization from ethanol (EtOH) and the solid obtained was collected by filtration and dried. The final product was 2-Boc-amino-6-chloropyridine in a yield of 29.2 g in 95% yield. The product was characterized by ESI-MS: m/z = 228 (M+) and HPLC retention time (Rt) was 1.70 min (Method C).
References
[1] Patent: US2011/21500, 2011, A1. Location in patent: Page/Page column 45
[2] Patent: US2011/172218, 2011, A1. Location in patent: Page/Page column 29
[3] Patent: US2012/149698, 2012, A1. Location in patent: Page/Page column 26
[4] Journal of Organic Chemistry, 2005, vol. 70, # 5, p. 1771 - 1779
[5] Patent: US2009/258877, 2009, A1. Location in patent: Page/Page column 16-17
