benzimidazole

Benzimidazole
IUPAC name	1H-benzimidazole
Identifiers
CAS number	51-17-2 Y
PubChem	5798
SMILES	n2c1ccccc1nc2
InChI	1/C7H6N2/c1-2-4-7-6(3-1)8-5-9-7/h1-5H,(H,8,9)
InChI key	HYZJCKYKOHLVJF-UHFFFAOYAX
ChemSpider ID	5593
Properties
Molecular formula	C7H6N2
Molar mass	118.14 g mol−1
Melting point	170–172 °C
Hazards
MSDS	External MSDS
EU classification	Harmful (Xn)
R-phrases	R20 R21 R22 R36 R37 R38
S-phrases	S26 S36
Y (what is this?)  (verify) Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa)
Infobox references

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.^[1]

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.^[2][3]

Preparation

Benzimidazole is commercially available. The usual synthesis involves condensation of o-phenylenediamine with formic acid,^[4] 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.^[4]

See also

• Benzimidazoline
• 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
• polybenzimidazole, a high performance fiber

References

Further reading

• Grimmett, M. R. (1997). Imidazole and benzimidazole synthesis. Boston: Academic Press. ISBN 0-12-303190-7.