Debromination of 5-Bromo-6-hydroxyquinoline and 7-Hydroxy-8-bromoquinoline with Hydrobromic Acid and Phenol

Application of 10%, 20%, or 48% hydrobromic acid to 5-bromo-6-hydroxyauinoline (I) or 7-hydroxy-8-bromoquinoline (II) resulted in recovery of the starting material in either case. The same reaction carried in the presence of phenol was found to cause quantitative debromination in the case of (I) and 48% hydrobromic acid and a debrominated compound was obtained in a high yield from (II) and 20% hydrobromic acid. The same was true in the case of 5-bromo-6-aminoquinoline and 20% hydrobromic acid with phenol. Debromination did not occur in the case of 6-hydroxy-7-bromoquinoline (V) and hydrobromic acid, even in the presence of phenol.