Synthesis
Synthesis of ethyl 4-chloroquinoline-3-carboxylate (A2): ethyl 4-hydroxyquinoline-3-carboxylate (A1) (1.5 g, 7 mmol) solid was placed in a reaction vial and phosphorus oxychloride (POCl3) (2.2 g, 1.3 mL, 14 mmol) was added. The reaction mixture was heated at 110 °C for 20 min. Upon completion of the reaction, the mixture was slowly poured into a pre-cooled mixture of aqueous ammonia solution (28-30%) and ice and stirred until a granular solid was formed. The reaction mixture was extracted with ether (3 x 40 mL), the organic layers were combined, dried with anhydrous magnesium sulfate (MgSO4), filtered and concentrated under reduced pressure to give an oily product. After standing, the product crystallized (1.44 g, 6 mmol, 87% yield) and could be used for subsequent reactions without further purification.
References
[1] Journal of Medicinal Chemistry, 2006, vol. 49, # 21, p. 6351 - 6363
[2] Patent: WO2005/123686, 2005, A1. Location in patent: Page/Page column 75-76
[3] European Journal of Medicinal Chemistry, 2015, vol. 103, p. 1 - 16
[4] Patent: CN108623589, 2018, A. Location in patent: Paragraph 0142; 0149
[5] Patent: CN108623581, 2018, A. Location in patent: Page/Page column 7
