Benzimidazole

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.

It is produced commercially as an parasiticide. The usual synthesis involves condensation of trimethylorthoformate and o-phenylenediamine:
 * C6H4(NH2)2 +  HC(OCH3)3  &rarr;  C6H4N(NH)CH  +  3 CH3OH

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.