3543-72-4

64-17-5

31349-48-1

3543-72-4

157 g (596.4 mmol) of 1-methyl-5-nitro-1H-benzimidazole-2-butanoic acid was suspended in 1374 g of ethanol, 43.8 g of 96% sulfuric acid was added and the reaction mixture was heated to 50 °C. After refluxing the reaction for 10 hours, the mixture was concentrated to a crystalline concentration. The catalytic acid was neutralized with triethylamine and crystallization was promoted by cooling, followed by filtration to collect the precipitate. The product, ethyl 1-methyl-5-nitro-1H-benzimidazole-2-butanoate, was washed with ethanol and dried to give 163 g (559.5 mmol) with a purity of >99% (yield 93.8% of the theoretical value).