Recent achievements in the synthesis of benzimidazole derivatives

Benzimidazoles are a class of heterocyclic compounds in which a benzene ring is fused to the 4 and 5 positions of an imidazole ring. Benzimidazole refers to the parent compound, while benzimidazoles are a class of heterocyclic compounds having similar ring structures, but different substituents. Benzimidazole derivatives possess a wide range of bioactivities including antimicrobial, anthelmintic, antiviral, anticancer, and antihypertensive activities. Many compounds possessing a benzimidazole skeleton have been employed as drugs in the market. The application of benzimidazoles in other fields has also been documented. The synthesis of benzimidazole derivatives has attracted much attention from chemists and numerous articles on the synthesis of this class of heterocyclic compound have been reported over the years. The condensation between 1,2-benzenediamine and aldehydes has received intensive interest, while many novel methods have been developed. In this article, we will give a comprehensive review of studies on the synthesis of benzimidazole, which date back to 2013. We have also tried to describe reaction mechanisms as much as we can. The work might be useful for chemists who work in the synthesis of heterocycles or drug chemistry.

Highly Fluorescent Cadmium Based Metal-Organic Frameworks for Rapid Detection of Antibiotic Residues, Fe3+ and Cr2O72- Ions

Here, two novel 3D Cd(II)-MOFs, [Cd₃·L·(BTB)₂·2DMF] and [(Cd₃O₂)·L·BTC] (denoted as CUST-532 and CUST-533, L = 9,10-bis(N-benzimidazolyl)-anthracene, BTB = 1,3,5-tris(4-carboxyphenyl) benzene, BTC = 1,3,5-benzenetricarboxylic acid, CUST = Changchun University of Science and Technology), were synthesized by solvothermal conditions. Both CUST-532 and CUST-533 are 3D (3,8)-c topological nets with the same point symbol of {4³}₂{4⁶·6¹⁸·8⁴}. PXRD and TGA analyses prove that CUST-532 and CUST-533 have good structural stability and thermal stability. On the basis of the high fluorescence characteristics, the results of fluorescence sensing experiments show that CUST-532 and CUST-533 can be used as multifunctional chemical sensors to achieve rapid fluorescence quenching response to antibiotic residues, Fe³⁺ and Cr₂O₇^2- ions at a much lower concentration. Furthermore, the possible mechanisms of fluorescence quenching in the sensing process were systematically studied by PXRD, UV-vis, fluorescence decay lifetime, and density functional theory.

Copper(i)–iodide cluster structures as functional and processable platform materials

This review provides a complete overview of the progress towards implementation of CuI-nanoclusters in functional materials and devices.

A Task-Specific Ionic-Liquid-Mediated Solvent-Free Protocol for Direct Access to Dimethyl Acetal Protected Benzimidazole 2-Carboxaldehydes

A robust and straightforward protocol has been developed for the synthesis of a diverse array of dimethyl acetal protected benz­imidazole-2-carboxaldehydes by reacting various 2-amino aniline derivatives with methyl 4,4-dimethoxy-3-oxobutanoate using the task-specific­ imidazolium ionic liquid (HBIm·TFA) as a promoter for N-C/C-N annulation processes. The present protocol offers several advantages over existing protocols, such as single-step process, short reaction times, very mild reaction conditions, high yields, ease of purification, recovery and reusability of the catalyst, and scale-up of the reaction.

One-dimensional Cu(I) and Ag(I) ladder-like coordination polymers supported by 2-ethyl-1-(pyridin-3-ylmethyl)-1H-benzimidazole

The title complexes, poly[[bis[μ2-2-ethyl-1-(pyridin-3-ylmethyl)-1H-benzimidazole-κ(2)N(1):N(3)]copper(I)] tetrafluoroborate acetonitrile monosolvate], {[Cu(C15H15N3)2]BF4·CH3CN}n, (I), and poly[[bis[μ2-2-ethyl-1-(pyridin-3-ylmethyl)-1H-benzimidazole-κ(2)N(1):N(3)]silver(I)] perchlorate methanol monosolvate], {[Ag(C15H15N3)2]ClO4·CH3OH}n, (II), are isostructural and exhibit one-dimensional ladder-like structures in which each asymmetric unit contains one metal ion (Cu(+) or Ag(+)), two 2-ethyl-1-(pyridin-3-ylmethyl)-1H-benzimidazole (bep) ligands, one counter-anion (tetrafluoroborate or perchlorate) and one interstitial molecule (acetonitrile or methanol). Each metal ion exhibits a distorted tetrahedral coordination geometry consisting of two pyridyl and two benzimidazole N atoms from four distinct ligands. Two metal ions are linked by two bep ligands to form a centrosymmetric 18-membered M2(bep)2 metallacycle, while adjacent M2(bep)2 metallacycles are further interlinked by another two bep ligands resulting in a ladder-like array. In the extended structure, four adjacent ladder-like arrays are connected together through C-H···F, O-H···O and C-H···O hydrogen bonds between bep ligands, solvent molecules and counter-anions into a three-dimensional supramolecular structure.

Synthesis of glycal-based chiral benzimidazoles by VO(acac)2-CeCl3 combo catalyst and their self-aggregated nanostructured materials

VO(acac)(2)-CeCl(3) combo catalyst has been developed for chemoselective cyclocondensation cum oxidation under mild reaction conditions toward synthesis of a new class of optically pure compounds, 2-(2'-C-3',4',6'-tri-O-benzyl/methyl-glycal)-1H-benzimidazoles. It involves an operationally simple synthetic protocol efficient for the syntheses of a wide range of chiral benzimidazoles in high yields without formation of undesired 1,2-disubstituted and pseudoglycal byproducts. Vanadium(V) is found as active oxidant for the chemical processes which is investigated by UV absorption spectroscopy. Highly ordered one-dimensional low molecular mass organic nanostructured materials are fabricated by nanocrystallization of the chiral nanoscale building blocks. Theoretical calculation by the B3LYP/6-31G** level of theory of the glycal-based chiral benzimidazoles shows out of planar geometry of the 1H-anthra[1,2-d]imidazole-6,11-dione moiety, which is responsible for the strong self-aggregation to generate ultralong nanostructured materials. We have also found nice agreement between the theoretical results with the experimental observation in 2D-NOESY experiments. The photophysical property of the solid nanostructured materials is also reported.

catena-Poly[[[diiodidocadmium(II)]-μ-1-(4-pyridylmeth-yl)-1H-benzimidazole] methanol hemisolvate]

In the title coordination polymer, {[CdI₂(C₁₃H₁₁N₃)]·0.5CH₄O}_n, each Cd^II center is four-coordinated by two N-atom donors from two 1-(4-pyridylmeth­yl)-1H-benzimidazole (L) ligands and two iodide anions, forming a tetra­hedral coordination geometry. L ligands bridge adjacent Cd^II ions, generating two crystallographically independent approximately orthogonal one-dimensional chains. The methanol solvent mol­ecule associates with one of the chains via O—H⋯I inter­actions.

catena-Poly[[diazido-manganese(II)]bis-[μ-1-(4-pyridylmeth-yl)-1H-benzimidazole]]

In the title polymeric compound, [Mn(N(3))(2)(C(13)H(11)N(3))(2)](n), each Mn(II) centre is six-coordinated in an octahedral geometry by six N atoms from four 1-(4-pyridylmeth-yl)-1H-benzimidazole (L) ligands and two azide anions (N(3) (-)). Each of the Mn(II) ions lies on an inversion centre. The L ligands and N(3) (-) anions bridge adjacent Mn(II) centres, generating a polymeric chain running along the [110] direction. Adjacent polymeric chains are arranged in a two-dimensional network parallel to the (001) plane, linked by C-H⋯N hydrogen bonds.

4,4'-Bis(benzimidazol-1-yl)biphen-yl

The mol­ecule of the title compound, C₂₆H₁₈N₄, resides on a crystallographic inversion centre with a dihedral angle of 44.94 (5)° between the benzimidazole ring system and the benzene ring. The primary hydrogen bond is C—H⋯N and inversion-related pairs of these generate a chain of rings along the c-axis direction; π⋯π stacking involving the benzimidazole groups with inter­planar separations of ca 3.4 Å complete the inter­actions.