1,3-Thiazole-5-carboxaldehyde oxime (2.5 g, 19.5 mmol, 1 eq.) was used as a starting material, which was dissolved in 12 mL of dioxane, followed by the addition of triethylamine (TEA, 6.8 mL, 2.5 eq.). The reaction mixture was cooled to 0 °C and trifluoroacetic anhydride (3.0 mL, 1.1 eq.) was added slowly and dropwise. The reaction solution was stirred overnight at room temperature and then trifluoroacetic anhydride (1.1 eq.) was added again to ensure complete reaction. Stirring was continued overnight at room temperature followed by solvent evaporation. The residue was dissolved in dichloromethane (DCM) and washed five times with water. The organic layer was dried over anhydrous magnesium sulfate (MgSO4) and concentrated under reduced pressure to give 1.25 g of 1,3-thiazole-5-carbonitrile in 58% yield.
