(2-Trifluoromethyl-pyridin-3-yl)-methanol (0.05 g, 0.28 mmol) was used as starting material and dissolved in anhydrous dichloromethane (10 mL). Subsequently, manganese dioxide (0.7 g, 8.0 mmol) was added to the solution. The reaction mixture was stirred under reflux conditions for 4 hours. Upon completion of the reaction, the mixture was cooled to room temperature and filtered through diatomaceous earth. The filtrate was concentrated by rotary evaporator to afford the target product 2-(trifluoromethyl)pyridine-3-carboxaldehyde as a yellow oil (0.035 g, 71% yield), which could be used in subsequent steps without further purification. The structure of the product was confirmed by 1H-NMR (400 MHz, CDCl3) and mass spectrometry (ESI+): 1H-NMR δ 10.40 (s, 1H), 8.83 (d, J = 4.7 Hz, 1H), 8.37 (d, J = 8.0 Hz, 1H), 7.63 (dd, J = 8.0 and 4.7 Hz, 1H); MS (ESI+): m/ z (M + H)+ = 176.
