Hydrochloric Acid → 4-Bromoquinoline-6-carboxylic acid

Methyl 4-bromo-6-quinolinecarboxylate (6.00 g) was dissolved in methanol (60 ml) and tetrahydrofuran (40 ml). A 1N aqueous sodium hydroxide solution (30 ml) was added to the solution while stirring at room temperature and the mixture was stirred at room temperature for 3 hr. A1N aqueous sodium hydroxide solution (20 ml) was added and the mixture was heated under reflux for 2 hr. The reaction mixture was adjusted to pH 4 with 1N hydrochloric acid. The resulting solid was collected by filtration and washed with water and ether to give 4-bromo-6-quinolinecarboxylic acid (4.65 g) as a white powder.