Step 2. Synthesis of 5-methyl-3-pyridinecarboxaldehyde. A mixture of 5-methyl-3-pyridinemethanol (106 mg, 0.86 mmol) with activated MnO2 (376 mg) in dichloromethane (10 mL) was reacted at room temperature with stirring overnight. Upon completion of the reaction, the MnO2 black solid was removed by filtration. The filtrate was concentrated under reduced pressure to afford 5-methylpyridine-3-carbaldehyde as a colorless oil (100 mg, 85% yield). The product was characterized by 1H NMR (CDCl3): δ 10.10 (s, 1H), 8.89 (s, 1H), 8.68 (s, 1H), 7.98 (s, 1H), 2.45 (s, 3H).
