BROMINE-LITHIUM EXCHANGE ON BROMO-8-HYDROXYQUINOLINES VIA FORMATION OF THEIR SODIUM-SALTS

A short and versatile method is reported for the preparation of 8-hydr oxyquinoline derivatives by reaction of n-butyllithium with 5,7-dibrom o-g-hydroxyquinoline 2 and 7-bromo-8-hydroxyquinoline 1 as their sodiu m salts. Thus, bromine-lithium exchange reaction on compound 2, highly regioselective, gave after addition of various electrophiles, 5-subst ituted 7-bromo-8-hydroxyquinolines 4a-j in moderate to good yields. Th e same procedure was also applicable to 7-bromo-8-hydroxyquinoline 1 w hich led to 7-substituted 8-hydroxyquinolines 3a-b.