148-24-3

6541-19-1

General procedure for the synthesis of 6,7-dichloroquinoline-5,8-dione from 8-hydroxyquinoline: sodium chlorate (0.50 mol) was slowly added to a solution of 8-hydroxyquinoline (0.10 mol) dissolved in concentrated hydrochloric acid (600 mL) over a period of 1 hour. The reaction mixture was stirred continuously at 40°C for 2 hours. Subsequently, the reaction solution was diluted with water to a total volume of 2 L. The resulting white precipitate was removed by filtration and discarded. The filtrate was extracted several times with dichloromethane (6 x 250 mL), all organic phases were combined, washed with water and concentrated under reduced pressure to give a yellow solid product. The solid product was recrystallized in methanol to give the final 6,7-dichloroquinoline-5,8-dione (compound 7) as bright yellow crystals. The characterization data of compound 7 was in agreement with that reported in literature [32].