How is 2-Chloro-1,6-naphthyridine (CAS: 23616-33-3) typically synthesized?

2-Chloro-1,6-naphthyridine is typically synthesized by the condensation of 1,6-diaminonaphthalene with thionyl chloride. This reaction involves the use of thionyl chloride in glacial acetic acid as a solvent. The yield is moderate, and the product is purified by recrystallization from an appropriate solvent. This method ensures good control over the purity and crystallinity of the final product.