Anhydrous dioxane (35 mL) was added to a mixture of 2-hydroxy-4-methylpyridine (2.10 g, 19.2 mmol) and selenium dioxide (2.50 g, 22.5 mmol). The heterogeneous solution was refluxed under argon for 48 hours. The mixture was cooled to room temperature. The mixture was treated with sodium bicarbonate (1.5 g). The mixture was stirred for 3 hours to neutralize acidic byproducts. The resulting dark brown suspension was filtered through a pad of magnesium sulfate (2.5 g), Florisic (2.5 g), and diatomaceous earth (2.5 g) to remove insoluble residues. The yellow filtrate was concentrated under vacuum to give the crude compound (1.40 g). The crude product was purified by silica gel column chromatography in ethyl acetate and 9:1 ethyl acetate/methanol to obtain 2-Hydroxy-4-pyridinecarboxaldehyde.
