6-Chloro-8-hydroxyquinoline

52671-64-4

56-81-5

18119-24-9

Step 4: In a 500mL three-necked flask equipped with a mechanical stirrer and reflux condenser, a solution of ferrous sulfate (2.0 g), 4-amino-3-chlorophenol hydrochloride (6.4 g, commercially available), nitrobenzene (2.9 mL), and boric acid (3.0 g) in glycerol (16 g) were added sequentially. Subsequently, concentrated sulfuric acid (9 mL) was added slowly and dropwise under cooling conditions. The ice bath was removed and replaced with an oil bath, and the reaction mixture was cautiously heated to 120 °C, maintained at this temperature for 2 h, and then heated up to 150 °C with continued stirring for 20 h. The reaction mixture was then heated up to 150 °C with continued stirring. Upon completion of the reaction, the mixture was cooled, decanted onto crushed ice and the resulting solution was neutralized with K2CO3. The product precipitated as a light brown solid, which was separated by filtration, washed sequentially with water and hexane, and finally dried in a vacuum oven at 35 °C overnight to obtain 7 g (77% yield) of the target product 8-chloro-6-hydroxyquinoline. Mass spectrum (ES) m/z (relative intensity): 180 ([M+H]+, 100).