General method: To a stirred solution of 4-methylquinoline-N-oxide (0.1 M) in anhydrous CH2Cl2 was added POBr3 (1.2 eq.) under argon protection at 0 °C, followed by dropwise addition of DMF (0.5 eq.). The reaction mixture was gradually warmed to 25 °C and stirred continuously for several hours until TLC showed that the reaction was complete. Saturated aqueous sodium carbonate solution was slowly added to the reaction mixture and the pH was adjusted to 7-8. The mixture was separated and the aqueous phase was thoroughly extracted with CH2Cl2. The organic phases were combined, washed with brine, dried with Na2SO4, filtered and concentrated under reduced pressure to give the crude product. The crude product was purified by fast column chromatography with PE/EA (100:1) as eluent.
