}} Benzimidazole is a heterocyclic aromatic organic compound. This bicyclic compound consists of the fusion of benzene and imidazole. The most prominent benzimidazole compound in nature is N-ribosyl-dimethylbenzimidazole, which serves as an axial ligand for cobalt in vitamin B12.

Benzimidazole, in an extension of the well-elaborated imidazole system, has been used as carbon skeletons for N-heterocyclic carbenes. The NHCs are usually used as ligands for transition metal complexes. They are often prepared by deprotonating an N,N'-disubstituted benzimidazolium salt at the 2-position with a base.

Preparation

Benzimidazole is commercially available. The usual synthesis involves condensation of o-phenylenediamine with formic acid, or the equivalent trimethyl orthoformate:

C₆H₄(NH₂)₂ + HC(OCH₃)₃ → C₆H₄N(NH)CH + 3 CH₃OH

By altering the carboxylic acid used, this method is generally able to afford 2-substituted benzimidazoles.

See also

• Albendazole, a common use anthelmintic.
• Indole, an analog with CH in place of nitrogen in position 3.
• Purine, an analog with two additional nitrogen atoms in the six-membered ring.
• Simple aromatic rings
• Triclabendazole, most common drug against liver flukes

References

Further reading

• Grimmett, M. R. (1997). Imidazole and benzimidazole synthesis. Boston: Academic Press.