Dabigatran etexilate related substance and preparation method thereof

The invention discloses a dabigatran etexilate related substance 2-{[4-(amino-n-hexyloxyimido-methylene)-phenylimino]-methylene}-1-methyl-1hydro-benzimidazole-5-ethyl formate (I) and a synthesis method thereof. The synthesis method comprises the following reaction procedures: under the action of acid and alcohol, enabling 2-{[4-(amino-n-hexyloxyimido-methylene)-phenylimino]-methylene}-1-methyl-1hydro-benzimidazole-5-ethyl formate (V) to react so as to generate acid salt (VI) of 2-{[4-(ethoxyimino)-phenylimino]-methylene}-1-methyl-1hydro-benzimidazole-5-ethyl formate; performing ammonification reaction on the compound (VI) to obtain acid salt (VII) of 2-[4-(imidophenylimino)-methylene]-1-methyl-1hydro-benzimidazole-5-ethyl formate; and enabling the compound (VII) to react with n-hexyl chloroformate to obtain the 2-{[4-(amino-n-hexyloxyimido-methylene)-phenylimino]-methylene}-1-methyl-1hydro-benzimidazole-5-ethyl formate (I).