General procedure for the synthesis of 4-bromo-5-methoxyquinoline from 4-hydroxy-5-methoxyquinoline: 4-hydroxy-5-methoxyquinoline (3.2 g, 18 mmol) was dissolved in DMF (22 ml) and phosphorus tribromide (2.2 ml) was added slowly. The reaction mixture was stirred at room temperature for 2 h. After that, it was slowly poured into water and neutralized with saturated aqueous sodium bicarbonate to pH 7-8. Subsequently, the precipitate was collected by filtration and washed several times with deionized water, and finally dried in vacuum drying oven to give the yellow solid product 4-bromo-5-methoxyquinoline (3.6 g, 85% yield). Mass spectrometric analysis (positive ion electrospray mode) showed m/z 239 [M+H]+.
