Synthesis
1. Carbon tetrachloride (35 mL) solution of bromine (2.25 mL, 43.7 mmol) was added dropwise to carbon tetrachloride (200 mL) solution of 1,6-naphthyridine (4.73 g, 36.4 mmol) under stirring conditions through a charging funnel.
2. The reaction mixture was heated to reflux for 1 hour.
3. Under reflux conditions, slowly add a dropwise solution of pyridine (2.94 mL, 36.4 mmol) in carbon tetrachloride (30 mL) to the reaction mixture and continue refluxing overnight.
4. Upon completion of the reaction, the reaction mixture was cooled and filtered.
5. Digest the solid with 1 M sodium hydroxide solution (200 mL) for 1 hour.
6. The basic aqueous phase was extracted with dichloromethane (2 x 200 mL), the organic phases were combined, dried over anhydrous sodium sulfate and concentrated.
7. The oil obtained was purified by column chromatography (eluent: 10% ethyl acetate/dichloromethane) to afford 8-bromo-1,6-naphthyridine (2.03 g, 27% yield) as yellow crystals with a melting point of 79-81°C. The solid was extracted with sodium hydroxide solution (2 x 200 mL) for 1 hour.
References
[1] Chemical & Pharmaceutical Bulletin, 1986, vol. 34, # 5, p. 2018 - 2023
[2] Patent: EP1147083, 2004, B1. Location in patent: Page 47
[3] Synthesis, 2007, # 8, p. 1185 - 1196
