General method: Step B: 1-methyl-6-nitro-1H-benzo[d]imidazole or 1-methyl-5-nitro-1H-benzo[d]imidazole is dissolved in methanol (or a solvent mixture of methanol and tetrahydrofuran), followed by the addition of 10% palladium/carbon catalyst. The reaction mixture was stirred at room temperature in a hydrogen atmosphere until thin layer chromatography (TLC) monitoring showed complete consumption of the feedstock. Upon completion of the reaction, the crude reaction solution was filtered through a diatomaceous earth pad and the filter cake was washed well with methanol. The filtrate was concentrated under reduced pressure and the resulting products, 1-methylbenzimidazol-5-amine or 1-methyl-1H-benzimidazol-6-amine, could be used directly in the subsequent reaction or further purified by silica gel column chromatography to obtain higher purity products.
