The mother nucleus benzimidazole is composed of benzene and imidazole, and its molecular formula is C7H6N2.
In the molecule of vitamin B 12, 5,6-dimethylbenzimidazole is attached to the cobalt center as a base.
Like imidazole, benzimidazole is also a common raw material for preparing nitrogen heterocyclic carbene.
This kind of carbene is prepared by deprotonation of N, N'- disubstituted benzimidazole at 2- position with alkali, and is used to prepare transition metal carbene complexes.
Benzimidazole is prepared by condensation of o-phenylenediamine with formic acid or trimethyl orthoformate;
c6h 4(NH2)2+HC(och 3)3→C6H4N(NH)CH+3 CH3OH
2- substituted benzimidazoles can be prepared by this method with other carboxylic acids.