The general procedure for the synthesis of 5,7-dibromo-8-hydroxyquinoline and 7-bromo-8-hydroxyquinoline from 8-hydroxyquinoline was as follows: bromination was carried out according to the method described in the literature [19]. This was done as follows: 8-hydroxyquinoline (2 mmol, 1 eq.) was dissolved in distilled CHCl3 (15 mL) at room temperature and protected from light, followed by the slow addition of different equivalents of molecular bromine (dissolved in CHCl3) over a period of 10 min. The reaction mixture was stirred continuously for 2 days, during which the progress of the reaction was monitored by TLC. Upon completion of the reaction, the organic layer was washed with 5% NaHCO3 solution (3 x 20 mL), dried over anhydrous Na2SO4 and concentrated under reduced pressure. Finally, the target product was separated by alumina column chromatography with ethyl acetate/hexane (1:5, 150 mL) as eluent.
