1.6 M n-butyllithium (0.9 mL, 1.4 mmol) was added slowly and dropwise to a tetrahydrofuran (THF, 10 mL) solution of 1-methyl-1H-1,2,3-triazole (32.0 mg, 1.2 mmol) at -78 °C, ensuring that the reaction temperature was maintained below -60 °C. After the reaction mixture was stirred continuously at -78 °C for 30 min, N,N-dimethylformamide (0.14 mL, 1.8 mmol) was added. Subsequently, the reaction system was slowly warmed to room temperature and stirring was continued for 1 hour. Upon completion of the reaction, the reaction was quenched with water and extracted with ethyl acetate (3 × 10 mL). The organic phases were combined, washed with water (3 x 10 mL), dried over anhydrous magnesium sulfate and concentrated under reduced pressure. The crude product was purified by silica gel column chromatography with an eluent ratio of 95:5 to 100:0 dichloromethane to methanol, resulting in 1-methyl-1H-1,2,3-triazole-5-carboxaldehyde as a yellow oil (40 mg, 30% yield).1H NMR (CDCl3) data: δ 4.10 (s, 3H), 7.88 (s, 1H), 9.55 (s, 1H). 1H).
