How is 5-Bromo-8-chloro-1,7-naphthyridine (CAS: 909649-06-5) typically synthesized?

5-Bromo-8-chloro-1,7-naphthyridine (CAS: 909649-06-5) can be synthesized by a multistep process involving bromination and chlorination of naphthyridine. Commonly, the synthesis begins with naphthyridine, which is brominated using bromine in the presence of a Lewis acid like aluminum trichloride. The resulting brominated compound is then treated with phosphorus pentachloride to introduce the chlorine atom. This process requires careful control of reaction conditions to ensure high yield and selectivity.