General procedure for the synthesis of 6-bromoquinoline-3-carbaldehyde from (6-bromoquinolin-3-yl)methanol: (6-bromoquinolin-3-yl)methanol (716 mg, 2.70 mmol) was dissolved in dichloromethane (9 mL), manganese dioxide (705 mg, 8.12 mmol) was added, and the reaction was stirred at 20°C for 2 days. After completion of the reaction, the mixture was filtered through diatomaceous earth and the filtrate was concentrated under reduced pressure to afford the target product 6-bromoquinoline-3-carbaldehyde (577 mg, 63% yield).
