Benzimidazole is a

heterocyclic A heterocyclic compound or ring structure is a cyclic compound that has atoms of at least two different elements as members of its ring(s). Heterocyclic chemistry is the branch of organic chemistry dealing with the synthesis, properties, and ...

aromatic In chemistry, aromaticity is a chemical property of cyclic ( ring-shaped), ''typically'' planar (flat) molecular structures with pi bonds in resonance (those containing delocalized electrons) that gives increased stability compared to satur ...

organic compound In chemistry, organic compounds are generally any chemical compounds that contain carbon-hydrogen or carbon-carbon bonds. Due to carbon's ability to catenate (form chains with other carbon atoms), millions of organic compounds are known. The ...

. This bicyclic compound may be viewed as fused rings of the aromatic compounds

benzene Benzene is an organic chemical compound with the molecular formula C6H6. The benzene molecule is composed of six carbon atoms joined in a planar ring with one hydrogen atom attached to each. Because it contains only carbon and hydrogen atoms, ...

and

imidazole Imidazole (ImH) is an organic compound with the formula C3N2H4. It is a white or colourless solid that is soluble in water, producing a mildly alkaline solution. In chemistry, it is an aromatic heterocycle, classified as a diazole Diazole refers ...

. It is a colorless solid.

Preparation

Benzimidazole is produced by condensation of

o-phenylenediamine ''o''-Phenylenediamine (OPD) is an organic compound with the formula C6H4(NH2)2. This aromatic diamine is an important precursor to many heterocyclic compounds. It is isomeric with ''m''-phenylenediamine and ''p''-phenylenediamine. Preparation ...

with

formic acid Formic acid (), systematically named methanoic acid, is the simplest carboxylic acid, and has the chemical formula HCOOH and structure . It is an important intermediate in chemical synthesis and occurs naturally, most notably in some ants. Es ...

,. or the equivalent

trimethyl orthoformate Trimethyl orthoformate (TMOF) is the organic compound with the formula HC(OCH3)3. A colorless liquid, it is the simplest orthoester. It is a reagent used in organic synthesis for the formation of methyl ethers. The product of reaction of an aldeh ...

: :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.Robert A. Smiley "Phenylene- and Toluenediamines" in Ullmann's Encyclopedia of Industrial Chemistry 2002, Wiley-VCH, Weinheim.

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 A coordination complex consists of a central atom or ion, which is usually metallic and is called the ''coordination centre'', and a surrounding array of bound molecules or ions, that are in turn known as ''ligands'' or complexing agents. Many ...

. 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 respon ...

. Many pharmaceutical agents belong to the benzimidazole class of compounds. For example: *

Angiotensin II receptor blocker Angiotensin II receptor blockers (ARBs), formally angiotensin II receptor type 1 (AT1) antagonists, also known as angiotensin receptor blockers, angiotensin II receptor antagonists, or AT1 receptor antagonists, are a group of pharmaceuticals tha ...

s such as azilsartan,

candesartan Candesartan is an angiotensin receptor blocker used mainly for the treatment of high blood pressure and congestive heart failure. Candesartan has a very low maintenance dose. The metabolism for the drug is unique as it is a cascading prodrug. Can ...

, and

telmisartan Telmisartan, sold under the brand name Micardis among others, is a medication used to treat high blood pressure, heart failure, and diabetic kidney disease. It is a reasonable initial treatment for high blood pressure. It is taken by mouth. ...

. *

Anthelmintic Anthelmintics or antihelminthics are a group of antiparasitic drugs that expel parasitic worms (helminths) and other internal parasites from the body by either stunning or killing them and without causing significant damage to the host. They may a ...

agents such as

albendazole Albendazole (also known as albendazolum) is a broad-spectrum anthelmintic and antiprotozoal agent of the benzimidazole type. It is used for the treatment of a variety of intestinal parasite infections, including ascariasis, pinworm infection, h ...

ciclobendazole Ciclobendazole is an anthelmintic, that is a pharmaceutical drug against parasitic worms. It underwent a clinical trial in the 1970s, where it was found to be as effective as mebendazole in the treatment of hookworm infection and ascariasis, but s ...

fenbendazole Fenbendazole is a broad spectrum benzimidazole anthelmintic used against gastrointestinal parasites including: giardia, roundworms, hookworms, whipworms, the tapeworm genus '' Taenia'' (but not effective against ''Dipylidium caninum'', a common d ...

flubendazole Flubendazole is an anthelmintic. Its brand name is Flutelmium which is a paste manufactured by Janssen Pharmaceutica N.V. used by veterinarians for protection against internal parasites and worms in dogs and cats. Other brand names are Flubenol, ...

mebendazole Mebendazole (MBZ), sold under the brand name Vermox among others, is a medication used to treat a number of parasitic worm infestations. This includes ascariasis, pinworm infection, hookworm infections, guinea worm infections, hydatid disease, ...

oxfendazole Oxfendazole is a broad spectrum benzimidazole anthelmintic. Its main use is for protecting livestock against roundworm, strongyles and pinworms. Oxfendazole is the sulfoxide metabolite of fenbendazole. Oxfendazole is an anthelmintic (wormer) co ...

oxibendazole Oxibendazole is a benzimidazole drug that is used to protect against roundworms, strongyles, threadworms, pinworms and lungworm infestations in horses and some domestic pets. It is usually white to yellowish in appearance, and may take the form ...

triclabendazole Triclabendazole, sold under the brand name Egaten among others, is a medication used to treat fascioliasis and paragonimiasis. It is very effective for both conditions. Treatment in hospital may be required. It is taken by mouth with typically ...

, and

thiabendazole Tiabendazole (INN, BAN), also known as thiabendazole (AAN, USAN) or TBZ and the trade names Mintezol, Tresaderm, and Arbotect, is a preservative, an antifungal agent, and an antiparasitic agent. Uses Preservative Tiabendazole is used primar ...

. *

Antihistamine Antihistamines are drugs which treat allergic rhinitis, common cold, influenza, and other allergies. Typically, people take antihistamines as an inexpensive, generic (not patented) drug that can be bought without a prescription and provides re ...

s such as

astemizole Astemizole (marketed under the brand name Hismanal, developmental code R43512) was a second-generation antihistamine drug that has a long duration of action. Astemizole was discovered by Janssen Pharmaceutica in 1977. It was withdrawn from the ma ...

bilastine Bilastine is an antihistamine medication used to treat hives (urticaria) and inflammation of the eye (allergic conjunctivitis) caused by an allergy. It is a second-generation antihistamine and takes effect by selectively inhibiting the histami ...

, clemizole, emedastine,

mizolastine Mizolastine (Mizollen) is a once-daily, non-sedating Antihistamine#H1-antihistamines, antihistamine. It blocks H1 receptor, H1 receptors and is commonly fast-acting. It does not prevent the actual release of histamine from mast cells, it only pre ...

, and oxatomide. * Benzimidazole fungicides such as

benomyl Benomyl (also marketed as Benlate) is a fungicide introduced in 1968 by DuPont. It is a systemic benzimidazole fungicide that is selectively toxic to microorganisms and invertebrates, especially earthworms, but nontoxic toward mammals. Due to th ...

, carbendazim, fuberidazole, and

. * Benzimidazole opioids such as

bezitramide Bezitramide is an opioid analgesic. Bezitramide itself is a prodrug which is readily hydrolyzed in the gastrointestinal tract to its active metabolite, despropionyl-bezitramide. Bezitramide was discovered at Janssen Pharmaceutica in 1961. It is m ...

brorphine Brorphine is a piperidine-based opioid analgesic compound. Brorphine was originally discovered in a 2018 paper investigating functionally biased opioid compounds, with the intention of finding safer analgesics that produce less respiratory depre ...

clonitazene Clonitazene is an opioid analgesic of approximately three times the potency of morphine. It is related to etonitazene Etonitazene is an analgesic drug, first reported in 1957, that has been shown to have approximately 1,000 to 1,500 times the po ...

etodesnitazene Etodesnitazene (Desnitroetonitazene, Etazen, Etazene, Etazone) is a benzimidazole derived opioid analgesic drug, which was originally developed in the late 1950s alongside etonitazene and a range of related derivatives. It is many times less pote ...

etonitazene Etonitazene is an analgesic drug, first reported in 1957, that has been shown to have approximately 1,000 to 1,500 times the potency of morphine in animals. Because it is characterized by a strong dependency potential and a tendency to produce pr ...

etonitazepipne Etonitazepipne (N-Piperidino Etonitazene) is a benzimidazole derivative with opioid effects around 100 times more potent than morphine, which has been sold over the internet as a designer drug. See also * Etazene * Etonitazepyne * Isotonitazen ...

etonitazepyne Etonitazepyne (N-Pyrrolidino Etonitazene) is a benzimidazole derivative with potent opioid effects which has been sold over the internet as a designer drug and linked to numerous cases of overdose. See also * Etazene * Etonitazepipne * Isoto ...

isotonitazene Isotonitazene is a benzimidazole derived opioid analgesic drug related to etonitazene, which has been sold as a designer drug. It has only around half the potency of etonitazene in animal studies, but it is likely even less potent in humans as ...

metodesnitazene Metodesnitazene (also known as Metazene) is a benzimidazole derivative with opioid effects, though unlike related compounds such as metonitazene and etodesnitazene which are many times more potent, metodesnitazene is only around the same potency ...

, and

metonitazene Metonitazene is an analgesic compound related to etonitazene, which was first reported in 1957, and has been shown to have approximately 100 times the potency of morphine by central routes of administration, but if used orally it has been shown t ...

. *

Proton-pump inhibitor Proton-pump inhibitors (PPIs) are a class of medications that cause a profound and prolonged reduction of stomach acid production. They do so by irreversibly inhibiting the stomach's H+/K+ ATPase proton pump. They are the most potent inhibitors ...

s such as

dexlansoprazole Dexlansoprazole, sold under the trade name Dexilant among others, is a medication which reduces stomach acid. It is used to treat gastroesophageal reflux disease. Effectiveness is similar to other proton pump inhibitors (PPIs). It is taken by mou ...

esomeprazole Esomeprazole, sold under the brand name Nexium among others, is a medication which reduces stomach acid. It is used to treat gastroesophageal reflux disease, peptic ulcer disease, and Zollinger–Ellison syndrome. Effectiveness is similar to o ...

ilaprazole Ilaprazole (trade name Noltec) is a proton pump inhibitor (PPI) used in the treatment of dyspepsia, peptic ulcer disease (PUD), gastroesophageal reflux disease (GORD/GERD) and duodenal ulcer. It is available in strengths of 5, 10, and 20&nbs ...

lansoprazole Lansoprazole, sold under the brand name Prevacid among others, is a medication which reduces stomach acid. It is used to treat peptic ulcer disease, gastroesophageal reflux disease, and Zollinger–Ellison syndrome. Effectiveness is similar to ...

omeprazole Omeprazole, sold under the brand names Prilosec and Losec, among others, is a medication used in the treatment of gastroesophageal reflux disease (GERD), peptic ulcer disease, and Zollinger–Ellison syndrome. It is also used to prevent upper g ...

pantoprazole Pantoprazole, sold under the brand name Protonix, among others, is a proton pump inhibitor used for the treatment of stomach ulcers, short-term treatment of erosive esophagitis due to gastroesophageal reflux disease (GERD), maintenance of heali ...

rabeprazole Rabeprazole, sold under the brand name Aciphex, among others, is a medication that decreases stomach acid. It is used to treat peptic ulcer disease, gastroesophageal reflux disease, and excess stomach acid production such as in Zollinger–Elli ...

, and

tenatoprazole Tenatoprazole is a proton pump inhibitor drug candidate that was undergoing clinical testing as a potential treatment for reflux oesophagitis and peptic ulcer as far back as 2003. The compound was invented by Mitsubishi Tanabe Pharma and was lice ...

. *

Typical antipsychotic Typical antipsychotics (also known as major tranquilizers, and first generation antipsychotics) are a class of antipsychotic drugs first developed in the 1950s and used to treat psychosis (in particular, schizophrenia). Typical antipsychotics ma ...

s such as

benperidol Benperidol, sold under the trade name Anquil among others, is a typical antipsychotic primarily used to treat hypersexuality syndromes and can be used to treat schizophrenia. It is a highly potent butyrophenone derivative and is the most potent n ...

clopimozide Clopimozide (R-29,764) is a typical antipsychotic drug of the diphenylbutylpiperidine class. It is very potent and has an extremely long duration of action, lasting at least one week with a single dose. It was developed by Janssen Pharmaceutica ...

droperidol Droperidol (Inapsine, Droleptan, Dridol, Xomolix, Innovar ombination with fentanyl">fentanyl.html" ;"title="ombination with fentanyl">ombination with fentanyl is an antidopaminergic medication, drug used as an antiemetic (that is, to prevent o ...

, neflumozide, and oxiperomide, and

pimozide Pimozide (sold under the brand name Orap) is an antipsychotic 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 weight basis i ...

. * Other notable pharmaceutical agents which contain a benzimidazole group include

abemaciclib Abemaciclib, sold under the brand name Verzenio among others, is a medication for the treatment of advanced or metastatic breast cancers. It was developed by Eli Lilly and it acts as a CDK inhibitor selective for CDK4 and CDK6. It was designa ...

bendamustine Bendamustine, sold under the brand name Treanda among others, is a chemotherapy medication used in the treatment of chronic lymphocytic leukemia (CLL), multiple myeloma, and non-Hodgkin's lymphoma. It is given by injection into a vein. Common s ...

dabigatran Dabigatran, sold under the brand name Pradaxa among others, is an anticoagulant used to treat and prevent blood clots and to prevent stroke in people with atrial fibrillation. Specifically it is used to prevent blood clots following hip or kne ...

daridorexant Daridorexant, sold under the brand name Quviviq, is an orexin antagonist medication which is used for the treatment of insomnia. Daridorexant is taken by mouth. Side effects of daridorexant include headache, somnolence, and fatigue. The med ...

, and glasdegib. In printed circuit board manufacturing, benzimidazole can be used as an

organic solderability preservative Organic solderability preservative or OSP is a method for coating of printed circuit boards. It uses a water-based organic compound that selectively bonds to copper and protects the copper until soldering. The compounds typically used are from the ...

. Several dyes are derived from benzimidazoles.Horst Berneth "Methine Dyes and Pigments" in ''Ullmann's Encyclopedia of Industrial Chemistry'', 2008, Wiley-VCH, Weinheim.

Preparation

Reactions

Applications

See also

References

Further reading