General procedure for the synthesis of 1-methyl-1H-imidazole-4-carboxaldehyde: (1-methyl-1H-imidazol-4-yl)methanol (5 g, 44.6 mmol) was dissolved in acetone (50 mL) under nitrogen protection and manganese dioxide (19.38 g, 223 mmol) was added slowly. The reaction mixture was stirred at 60°C for 12 hours. After completion of the reaction, the solid was removed by filtration and the filtrate was concentrated to afford the crude product 1-methyl-1H-imidazole-4-carbaldehyde (4.12 g, 34.4 mmol, 77% yield), which could be used in the subsequent reaction without further purification. m/z 111.2 ([M+H]+) and retention time 0.49 min were obtained by LC-MS analysis.
