Synthesis
General procedure for the synthesis of 4-chloro-7-bromoquinoline from 4-hydroxy-7-bromoquinoline: Phosphorus oxychloride (106.76 g, 696.28 mmol) was added in batches to a solution of dioxane (660 mL) containing 4-hydroxy-7-bromoquinoline (60 g, 267.8 mmol) at 30 °C. The reaction mixture was stirred at 100 °C for 40 min before confirming that 4-hydroxy-7-bromoquinoline had been completely converted to 4-chloro-7-bromoquinoline by thin layer chromatography (TLC) monitoring. Upon completion of the reaction, the reaction was quenched with water (200 mL) and subsequently extracted with ethyl acetate (200 mL x 2). The combined organic phases were washed with saturated sodium chloride solution (100 mL x 2) and dried with anhydrous sodium sulfate. After concentration under reduced pressure, the target compound 4-chloro-7-bromoquinoline (light yellow solid, 59 g, 81.77% yield) was obtained. It was analyzed by liquid chromatography-mass spectrometry (LC-MS, ESI), and the molecular ion peak m/z was 243.8 ([M+H]+).
References
[1] Patent: EP3293177, 2018, A1. Location in patent: Paragraph 0459; 0460
[2] Journal of the American Chemical Society, 1949, vol. 71, p. 3236
[3] Journal of the American Chemical Society, 1946, vol. 68, p. 113,115
[4] Journal of Medicinal Chemistry, 1998, vol. 41, # 25, p. 4918 - 4926
[5] Patent: WO2018/34918, 2018, A1. Location in patent: Page/Page column 71
