1-methyl-2-nitro-1H-imidazole-5-carboxylic acid methyl ester 1c (50g, 0.27mol) was dissolve in 500mL tetrahydrofuran, followed by dropwise add methanol (13g, 0.4mol, 1.5eq) at 0 ℃. A solution of lithium hydride in tetrahydrofuran (2M, 202 mL, 1.5 eq) was added, and the reaction was incubated at 0 ℃ for 1 hour. The reaction solution was quenched by adding 500 mL of water, and extracted with ethyl acetate (500 mL × 3). The organic phases were combined, dried over anhydrous sodium sulfate, filtered, and concentrated under reduced pressure. The residue was added with dichloromethane (200 mL) and filtered to obtain 3-Methyl-2-nitro-3H-imidazole-4-carboxylic acid methyl ester(31 g, 0.2 mol, yellow solid), yield: 73%.
