Benzimidazole is a heterocyclic aromatic

organic compound Some chemical authorities define an organic compound as a chemical compound that contains a carbon–hydrogen or carbon–carbon bond; others consider an organic compound to be any chemical compound that contains carbon. For example, carbon-co ...

. This bicyclic compound may be viewed as fused rings of the aromatic compounds benzene and imidazole. It is a white solid that appears in form of tabular crystals.

Preparation

Benzimidazole was discovered during research on vitamin B₁₂. The benzimidazole nucleus was found to be a stable platform on which drugs could be developed. Benzimidazole is produced by condensation of o-phenylenediamine with formic acid, or the equivalent trimethyl orthoformate: :C₆H₄(NH₂)₂ + HC(OCH₃)₃ → C₆H₄N(NH)CH + 3 CH₃OH 2-Substituted derivatives are obtained when the condensation is conducted with aldehydes in place of formic acid, followed by

oxidation Redox ( , , reduction–oxidation or oxidation–reduction) is a type of chemical reaction in which the oxidation states of the reactants change. Oxidation is the loss of electrons or an increase in the oxidation state, while reduction is ...

Reactions

Benzimidazole is a base: :C₆H₄N(NH)CH + H⁺ → ₆H₄(NH)₂CHsup>+ It can also be deprotonated with stronger bases: :C₆H₄N(NH)CH + LiH → Li ₆H₄N₂CH + H₂ The imine can be alkylated and also serves as a ligand in coordination chemistry. The most prominent benzimidazole complex features ''N''-ribosyl-dimethylbenzimidazole, as found in vitamin B₁₂. ''N'',''N-Dialkylbenzimidazolium salts are precursors to certain ''N''-heterocyclic carbenes.

Applications

Benzimidazole derivatives are among the most frequently used ring systems for small molecule drugs listed by the United States

Food and Drug Administration The United States Food and Drug Administration (FDA or US FDA) is a List of United States federal agencies, federal agency of the United States Department of Health and Human Services, Department of Health and Human Services. The FDA is respo ...

. Many pharmaceutical agents belong to the benzimidazole class of compounds. For example: * Angiotensin II receptor blockers such as azilsartan, candesartan, and telmisartan. * Anthelmintic agents such as albendazole, ciclobendazole, fenbendazole, flubendazole, mebendazole, oxfendazole, oxibendazole, triclabendazole, and thiabendazole. These drugs work by binding tubulin, a vital part of the cytoskeleton and mitotic spindle. Benzimidazoles are selectively toxic towards parasitic nematodes, selectively binding and depolymerising their tubulins. * Antihistamines such as astemizole, bilastine, clemizole, emedastine, mizolastine, and oxatomide. * Benzimidazole fungicides such as benomyl, carbendazim, fuberidazole, and thiabendazole. These drugs selectively bind to and depolymerise fungal tubulin. * Benzimidazole opioids such as bezitramide, brorphine, clonitazene, etodesnitazene, etonitazene, etonitazepipne, etonitazepyne, isotonitazene, metodesnitazene, and metonitazene. * Proton-pump inhibitors such as dexlansoprazole, esomeprazole, ilaprazole, lansoprazole, omeprazole, pantoprazole, rabeprazole, and tenatoprazole. * Typical antipsychotics such as benperidol, clopimozide, droperidol, neflumozide, and oxiperomide, and

pimozide Pimozide (sold under the brand name Orap) is a neuroleptic medication, drug of the diphenylbutylpiperidine class. It was discovered at Janssen Pharmaceutica in 1963. It has a high potency compared to chlorpromazine (ratio 50-70:1). On a weigh ...

. * Other notable pharmaceutical agents which contain a benzimidazole group include abemaciclib, bendamustine, dabigatran, daridorexant, and glasdegib. In printed circuit board manufacturing, benzimidazole can be used as an organic solderability preservative. Several dyes are derived from benzimidazoles.

Preparation

Reactions

Applications

See also

References

Further reading