General procedure for the synthesis of ethyl 4-chloro-8-bromoquinoline-3-carboxylate from ethyl 4-hydroxy-8-bromoquinoline-3-carboxylate: ethyl 8-bromo-4-hydroxyquinoline-3-carboxylate (2.0 g, 6.75 mmol) was dissolved in phosphorus triclosan (10 mL) and heated to reflux for 3 hr at 80 °C. Upon completion of the reaction, volatiles were removed by distillation under reduced pressure and the residue was quenched with ice water. The precipitated solid was collected by filtration and dried to give 1.8 g of the target product ethyl 4-chloro-8-bromoquinoline-3-carboxylate. The structure of the product was confirmed by 1H NMR (300 MHz, DMSO-d6) and mass spectrometry: 1H NMR δ 9.26 (s, 1H), 8.44-8.37 (m, 2H), 7.79-7.64 (t, J = 7.8 Hz, 1H), 4.48-4.43 (q, J = 7.2, 14.1 Hz, 2H), 1.41-1.36 (t. J = 6.9 Hz, 3H); MS (m/z): 314.01 (M + H)+.
