A Simple and Efficient One-Pot Synthesis of 2-Substituted Benzimidazoles

Abstract

A simple and efficient procedure for the synthesis of substituted benzimidazoles through a one-pot condensation of o-phenylenediamines with aryl aldehydes in the presence of H 2 O 2 /HCl system in acetonitrile at room temperature is described. Short reaction time, large-scale synthesis, easy and quick isolation of the products, and excellent yields are the main advantages of this procedure.

Brønsted acid-catalyzed metal-free one-pot synthesis of benzimidazoles via [4+1] heteroannulation of ortho-phenylenediamines with β-oxodithioesters

“…The spectral data of all the products are in accordance with the literature [16][17][18][19][20][21][22] values. A plausible reaction mechanism for the domino annulation of ortho-phenylenediamine with β-oxodithioester is shown in Scheme 2.…”

“…13 Owing to the vast importance of benzimidazoles in drug discovery and other fields, enormous efforts have been made to develop the operationally simple and efficient synthetic methods for their construction. [14][15][16][17][18][19][20][21][22] Classical approaches to benzimidazoles derivatives involve coupling of 1,2-phenylenediamines with aldehydes/carboxylic acids/nitriles/ortho-esters and their derivatives under varying conditions. 23 …”

Direct conversion of alkyl halides into benzimidazoles using pyridine-N-oxide and 1,2-diaminobenzenes

“…The oxidizing agent carries out dehydrocyclization of an imine intermediate. Some of the most employed oxidants are hypervalent iodine, 35 hydrogen peroxide, 36 Oxone, 37 air, 38 lead tetraacetate, 39 potassium ferricyanide, 40 nitrogen dioxide and ozone, 41 zirconyl chloride octahydrate/ montmorillonite K-10, 42 . These procedures have important drawbacks such as laborious workup, difficult benzimidazole purification, toxic byproducts containing heavy metals and low yields.…”

Microwave-assisted practical and simple method for heterocyclization of o-phenylenediamine and aldehydes using DDQ as oxidant agent

“…Various oxidative agents such as 1,4-benzoquinone (18), MnO 2 (19), H 2 O 2 /HCl (20), benzofuroxane (21), 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ) (22), ceric (IV) ammonium nitrate (CAN) (23), NaHSO 3 (24), and polymer-supported hypervalent iodine (25) have been applied. On the other hand, it has been reported that the redox system can be used as the catalyst for the preparation of benzimidazoles.…”