2-Bromo-5-fluoropyrazine

374063-92-0

1209459-10-8

The general procedure for the synthesis of 2-bromo-5-fluoropyrazine using 2-bromo-5-hydroxypyrazine as starting material was as follows: 4.2 g (24 mmol) of 2-bromo-5-hydroxypyrazine was dissolved in 25 mL of pyridine and cooled to 0 °C in an ice bath. Subsequently, 8.12 g (28.8 mmol) of trifluoromethanesulfonic anhydride (Aldrich) was added in batches over about 5 minutes. The reaction mixture was stirred in an ice bath for 30 minutes, followed by stirring at room temperature overnight. Upon completion of the reaction, the reaction mixture was mixed with 300 mL of ether and 500 mL of aqueous 1N HCl. The organic and aqueous layers were separated and the aqueous layer was back-extracted with 200 mL of ether. The combined organic phases were washed sequentially with saturated aqueous NaHCO3 solution (2 x 100 mL) and saturated aqueous NaCl solution (200 mL). The organic layer was dried over anhydrous MgSO4, filtered and concentrated under reduced pressure to obtain the crude product. The crude product was purified by silica gel column chromatography (eluent: ethyl acetate/hexane) to afford 5.55 g (75% yield) of 2-bromo-5-fluoropyrazine. The structure of the product was confirmed by 1H NMR.