Under stirring conditions, 10.47 g (0.081 mol) of selenite was dissolved in 30 mL of water and the resulting solution was slowly added to a 150 mL solution of 1,4-dioxane containing 20 g (0.162 mol) of 6-methyl-2-pyridinemethanol (3a). The reaction mixture was stirred continuously at 100 °C for 6 hours. Upon completion of the reaction, the resulting metallic selenium was removed by filtration. The filtrate was distilled under reduced pressure to remove the solvent and the residue was treated by extraction with hot hexane (3 x 150 mL). After combining the extracts, the solvents were again removed by distillation under reduced pressure and the resulting product did not require further purification. Finally, 14.76 g (0.121 mol, 75% yield) of 6-methyl-2-pyridinecarboxaldehyde was obtained with a melting point of 31-33 °C. The product structure was determined by 1H NMR. The structure of the product was determined by 1H NMR (DMSO-d6, δ, ppm): 2.61 (s, 3H, Me), 7.49 (d, 1H, 5-H, J = 7.5 Hz), 7.71 (d, 1H, 3-H, J = 7.5 Hz), 7.86 (dd, 1H, 4-H, J = 7.5, 7.5 Hz), 9.93 (s, 1H, CHO) and mass spectrum (m/z 122.06, I rel 100% [M + H]+) confirmed that the calculated molecular weight was 122.06.
