HALOGENATION REACTIONS IN POSITION-3 OF QUINOLINE-2,4-DIONE SYSTEMS BY ELECTROPHILIC SUBSTITUTION AND HALOGEN EXCHANGE

3-Substituted 4-hydroxy-2(1 H)-quinolones 3, 5, 7 are halogenated with bromine or sulfuryl chloride to yield the quinolinediones 9 or 10. Reaction of 3, 5, 7 with chloroform gives the dichloromethyl quinolinediones 11. Halogen exchange leads from the chloro quinolinediones 10 to fluoro quinolinedones 12 and to azido quinolinediones 13. Similarly the dichloro quinolinedione 10 an reacts to the difluoro quinolinedione 14, which is reduced to the 3-fluoro-4-hydroxyquinolone 16 and reacts again with sulfuryl chloride to give the mixed 3-chloro-3-fluoroquinolinedione 15.