- Dehydrogenative synthesis of benzimidazoles under mild conditions with supported iridium catalysts
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Solid supported iridium catalysts, which show excellent activity for the dehydrogenative synthesis of benzimidazoles from primary alcohols and phenylenediamine derivatives under mild reaction conditions, were developed. Among the catalysts examined, the titania-supported iridium catalyst showed the highest activity, and benzimidazole derivatives were selectively produced at temperatures of 80°C or higher. For example, the reaction of phenylenediamine (1a) with benzyl alcohol (2a) in the presence of Ir(1.0 wt%)/TiO2 (1.0 mol%, towards 1a) at 120°C selectively gave 2-phenylbenzimidazole (3aa) in 80% yield after 6 h and over 90% yield after 18 h. A high turnover number (TON) of more than 800 was achieved in the reaction at a higher substrate-to-catalyst ratio. Reduction of the catalysts under a hydrogen atmosphere at around 500 to 600°C is essential for their significant activity. Characterization of the catalysts by gas adsorption, XRD, XPS, H2-TPR, TEM, and XAFS techniques revealed that highly-dispersed nanoparticles of the iridium(0) species (ca. 1 to 2 nm in diameter) formed on TiO2 are responsible for the catalysis. The catalysts could be recycled without a significant loss of activity, and the leaching of the iridium species into the solution during the catalytic runs was negligible, which suggests that the present catalysts would be excellent from both environmental and practical perspectives.
- Tateyama, Keisuke,Wada, Kenji,Miura, Hiroki,Hosokawa, Saburo,Abe, Ryu,Inoue, Masashi
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- Facile route for the synthesis of benzothiazoles and benzimidazoles in the presence of tungstophosphoric acid impregnated zirconium phosphate under solvent-free conditions
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Rapid and efficient condensation reactions of o-phenylenediamine and o-aminothiophenol with various aldehydes were carried out using tungstophosphoric acid impregnated zirconium phosphate in solvent-free conditions to afford the corresponding 2-substituted arylbenzimidazole and arylbenzothiazole derivatives in good to excellent yields. This procedure constitutes a simple and practical green synthetic method for 2-arylbenzimidazoles and 2-arylbenzothiazoles and their structural analogs. Furthermore, the catalyst can be reused for several times but it will be less active.
- Aliyan, Hamid,Fazaeli, Razieh,Fazaeli, Nahid,Mssah, Ahmad Reza,Naghash, Hamid Javaherian,Alizadeh, Mohammad,Emami, Ginous
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- An efficient and one-pot synthesis of imidazolines and benzimidazoles via anaerobic oxidation of carbon-nitrogen bonds in water
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The system, I2/KI/K2CO3/H2O, oxidizes carbon-nitrogen bonds for the synthesis of imidazolines and benzimidazoles from aldehydes and diamines under anaerobic conditions in water at 90°C with excellent yields. The process is green, mild and inexpensive.
- Gogoi, Pranjal,Konwar, Dilip
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- Preparation of 2-Arylbenzimidazole derivatives using CuO nanoparticles /H2O2 system
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CuO nanoparticles were prepared in watery lemon juice media and were characterized by XRD, FE-SEM, DLS, TGA and BET analysis. The as-prepared catalyst was efficient and recyclable for a high yielding, and practical method for the synthesis of 2-arylbenzimidazoles via cyclo-condensation reaction of 1,2-benzenediamine and aldehydes using copper oxide (CuO) nanoparticles is reported. Solvents and solvent-free effects on the reaction were investigated. Solvent plays a significant role in the reaction, and best results were achieved in solvent-free condition at 80°C. All reactions were completed in short reaction times (20–120?min) with 76–97% yields.
- Fazlinia, Abbas,Sheikh, Setareh
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- Efficient and high colour-purity green-light polymer light-emitting diodes (PLEDs) based on a PVK-supported Tb3+-containing metallopolymer
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Based on the free-radical copolymerization of the green-light complex monomer [Tb(eb-PMP)3(4-VB-PBI)] (2; Heb-PMP = 4-(2-ethylbutanoyl)-1-phenyl-3-methyl-1H-pyrazol-5(4H)-one; 4-VB-PBI = 1-(4-vinylbenzyl)-(pyridin-2-yl)-1H-benzo[d]imidazole) with NVK (N-vinylcarbazole), the obtained Tb3+-containing metallopolymer poly(NVK-co-2) with an energy transfer from additional PVK to Tb3+ ion was used as the emitting material of polymer light-emitting diodes (PLEDs); it exhibited record renewed efficiencies (24.63 cd A-1, 7.81%, and 6.45 lm W-1) of Tb3+-based extreme colour-purity green-light PLEDs and superior performance of colour-stability and low efficiency roll-off to small-molecule Tb3+-complex's OLEDs.
- Liu, Lin,Pang, Mengyuan,Chen, Hongting,Fu, Guorui,Li, Baoning,Lü, Xingqiang,Wang, Lei
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- Heteroleptic ruthenium(II) complexes of 2-(2-pyridyl)benzimidazoles: A study of catalytic efficiency towards transfer hydrogenation of acetophenone
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Six ruthenium(II) complexes ([RuCl2(p-cymene)(L1-6)], SD1-6, (L1-6: bidentate pyridyl-benzimidazole ligands)) were synthesized from [RuCl2(p-cymene)]2 dimer and bidentate pyridyl-benzimidazole ligands. The compounds were characterized by elemental analysis, IR, UV-Vis, NMR and X-ray diffraction. The synthesized Ru(II) complexes (SD1-6) were tested as catalysts for the catalytic transfer hydrogenation (CTH) of acetophenone to secondary alcohols in the presence of KOH using 2-propanol as a hydrogen source at 82 °C. All complexes were active catalysts for TH of acetophenone with good yields under mild conditions (after 15 min, yields of up to 91%).
- Dayan, Osman,Demirmen, Selin,?zdemir, Namik
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- Semi-empirical computation on mechanism of imidazolines and benzimidazoles synthesis and their QSAR studies
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A green, mild and anaerobic synthesis of imidazolines and benzimidazoles from aldehydes and diamines using I2/KI/K2CO3/H2O system has been investigated by semi-empirical methods. The observed efficient direction of the above synthesis has been modeled from a comparison of the energies of four possible transition states arising from mono and di additions of iodines in the configured molecules. In the reaction I1 B is the most favorable transition state [TS] which is shown to be 20 Kcal/mol by PM3 analyses. The resulting trends of relative transition states energies are in excellent agreement with the experimental observations. Also, the bond order, bond length, heat of formation is in good agreement to the formation of product B. In order to establish the suitable mechanism of the reaction a quantitative structure activity relationship analysis has been made using hydrophobicity as the molecular descriptor. In this analysis the values of refractivity, polarizability, hydration energy, electron affinity, ionization potential and dipole moment of the compounds have been correlated with their hydrophobicity which has been taken as the molecular property.
- Hazarika, Swapnali,Konwar, Dilip,Bora, Manas Jyoti
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- Reusable α-MoO3 nanobelts catalyzes the green and heterogeneous condensation of 1,2-diamines with carbonyl compounds
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Crystalline nanobelts of α-MoO3 have been obtained successfully using novel and safe agents through a simple and safe sol-gel method (polymerizing-complexing) and characterized by XRD, FT-IR, Raman spectroscopies, high resolution transmission electron microscopy (HRTEM), scanning electron microscopy (SEM) and the temperature programmed desorption (TPD) of ammonia. An orthorhombic lattice system for nano-MoO3 was established. The HRTEM images showed that the nanobelt morphology of α-MoO3 mostly ranged from 20-70 nm in width and 200-400 nm in length. The ammonia TPD profile demonstrated strong acidic sites. The spectral and analysis data confirmed the effectiveness of the method for the preparation of α-MoO3 nanobelts by prevention of grain growth or agglomeration of the particles. The nanostructured MoO3 exhibited a high efficiency in catalyzing the condensation reaction of various 1,2-diamine and carbonyl compounds for synthesis of heterocyclic compounds. The recovery of the title heterogenous nanocatalyst was easy and efficient and its catalytic activity was strikingly different from the bulk material.
- Jafarpour, Maasoumeh,Rezaeifard, Abdolreza,Ghahramaninezhad, Mahboube,Tabibi, Tooba
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- Mild and highly efficient protocol for the synthesis of benzimidazoles using samarium triflate [Sm(OTf)3]
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One-pot synthesis of benzimidazole compounds from ortho-phenylenediamine and a variety of aldehydes was developed under mild reaction conditions. All the reactions were carried out in the presence of samarium triflate (10mol%) in acetonitrile at room temperature. Copyright Taylor & Francis Group, LLC.
- Narsaiah, A. Venkat,Reddy, A. Ramesh,Yadav
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- Anticancer copper pyridine benzimidazole complexes: ROS generation, biomolecule interactions, and cytotoxicity
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The Cu(II) complex CuCl2(pbzH), pbzH = 2-(2-pyridyl)benzimidazole, and derivatives modified at the non-coordinated nitrogen of the benzimidazole fragment, have been studied as anticancer agents. These compounds show promising cytotoxicity against A549 adenocarcinomic alveolar basal epithelial cells with IC50 values in the range of 5–10 μM. Importantly, this activity is higher than either CuCl2·2H2O or the individual ligands, demonstrating that ligand coordination to the Cu(II) centres of the complexes is required for full activity. Electron paramagnetic resonance (EPR) and UV–Vis spectroscopies were used to characterize the solution behaviour of the complexes. These studies demonstrate: (i) two types of solvated species in buffer, (ii) both coordinate and non-coordinate interactions with albumin, and (iii) weak interactions with DNA. Further DNA studies using agarose gel electrophoresis demonstrate strand cleavage by the complexes in the presence of ascorbate, which is mediated by reactive oxygen species (ROS). Through a fluorescence-based in vitro assay, intracellular ROS generation in the A549 cell line was observed; indicating that damage by ROS is responsible for the observed activity of the complexes.
- Prosser, Kathleen E.,Chang, Stephanie W.,Saraci, Felix,Le, Phuc H.,Walsby, Charles J.
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- Electrocatalytic CO2 reduction using rhenium(I) complexes with modified 2-(2'-pyridyl)imidazole ligands
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The reduction of CO2 to CO is an ongoing chemical challenge of great interest for the development of renewable and sustainable technologies. Coordination complexes of rhenium(I) are widely known as CO2 reduction electrocatalysts, with emphasis on complexes bearing 2,2'-bipyridine (bpy) ligands. Recent research efforts have focused on incorporation of these catalysts into solid, electroactive supports, which can be challenging due to the requirement for synthetic modification to bpy ligands. Development of related ligand sets with modular syntheses is therefore an attractive goal. We investigated electrocatalytic CO2 reduction using ReCl(CO)3(N-N) complexes, where N-N is 2-(2'-pyridyl)imidazole (PyIm), 2-(2'-pyridyl)benzimidazole (PyBIm), 2-(2'-quinolyl)imidazole (QuIm), or 2-(2'-quinolyl)benzimidazole (QuBIm) ligands. In CO2-saturated MeCN solutions, cyclic voltammograms of the Re-QuBIm complex showed current enhancement at a peak potential of ?2.01 V vs. Cp2Fe+/0. The catalytic current was stable upon repeated cycling. Re-QuBIm has an overpotential ～200 mV lower than related Re-bpy catalysts, but also is kinetically slower. The redox reactivity of each complex can be correlated to electronic parameters of the N-N chelating ligands. These results suggest that modular reduction potential tuning of CO2 reduction catalysts is possible, but associated penalties to activity are important considerations.
- Sinha, Soumalya,Berdichevsky, Ellan K.,Warren, Jeffrey J.
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- Ti, Zr and v complexes with N-allyl functionalized heterocyclic ligands as catalysts for ethylene polymerization Dedicated to Professor Max Herberhold on the occasion of his 80th birthday (August 02, 2016).
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Titanium, zirconium and vanadium complexes with N-allyl functionalized 1,2-bis(benzimidazolyl)benzene, 1,2-bis(benzimidazolyl)ethane, 1,1-bis(benzimidazolyl)methane, 2,2-bis(benzimidazolyl), 2,6-bis(benzimidazolyl)pyridine and 2-(benzimidazolyl)pyridine ligands were synthesized and characterized. After activation with methylaluminoxane (MAO) they were applied for catalytic ethylene polymerization. The performance of such homogeneous catalysts is unique: they have high activities (up to 3278 kg PE/mol cat h), they produce bimodal or multimodal resins with high molecular weights and they have the potential to produce their own support for heterogeneous polymerization reactions. Such catalysts combine all features for single-reactor bimodal polyethylene technology.
- Elagab, Hamdi Ali,Alt, Helmut G.
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- High-efficiency electrophosphorescent copolymers containing charged iridium complexes in the side chains
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A convenient approach to novel charged Ir polymers for opto-electronic devices to achieve red emission was developed. 2-(Pyridin-2-yl)-benzimidazole units grafted into the side chains of macroligands (PFCz and PFP) served as ligands for the formation of charged Ir complex pendants with 1-phenylisoquinoline (1-piq). The charged Ir polymers (PFPIrPiq and PFCzIrPiq) showed exclusive Ir(1-piq)2(N-[2-(pyridin-2-yl)benzimidazole]hexyl) +BF4- (IrPiq) emission, with the peak at 595 nm. The best device performances were obtained from PFCzIrPiq4 with the device configuration of ITO/PEDOT:PSS/PFCzIr-Piq4+PBD (30 wt%)/TPBI/Ba/Al (PBD: 5-(4-tert-butylphenyl)-2-(bi-phenyl-4-yl)-1,3,4-oxadiazole; TPBI: 1,3,5-tris-(2-N-phenylbenzimidazolyl)-benzene). A maximum external quantum efficiency (EQE) of 7.3% and a luminous efficiency (LE) of 6.9 cd A-1 with a luminance of 138 cd m-2 were achieved at a current density of 1.9 mA cm-2. The efficiencies remained as high as EQE = 3.4% and LE = 3.3 cd A-1 with a luminance of 3770 cd m-2 at a current density of 115 mA cm-2. The single-layer devices based on charged Ir polymers also showed high efficiency with the high work-function metal Ag as cathode. The maximum external quantum efficiencies of the devices were 0.64 % and 0.66% for PFPIrPiq2 and PFPIrPiq10, respectively. A possible mechanism of an electrochemical cell associated with its electrochemical redox pathway for single-layer devices has been proposed. The results showed that the charged Ir polymers are promising candidate materials for polymer optoelectronic devices.
- Du, Bin,Wang, Lei,Wu, HongBin,Yang, Wei,Zhang, Yong,Liu, RanSheng,Sun, MingLiang,Peng, Junbiao,Cao, Yong
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- Iron sulfide catalyzed redox/condensation cascade reaction between 2-amino/hydroxy nitrobenzenes and activated methyl groups: A straightforward atom economical approach to 2-hetaryl-benzimidazoles and -benzoxazoles
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Iron sulfide generated in situ from elemental sulfur and iron was found to be highly efficient in catalyzing a redox/condensation cascade reaction between 2-amino/hydroxy nitrobenzenes and activated methyl groups. This method represents a straightforward and highly atom economical approach to 2-hetaryl-benzimidazoles and -benzoxazoles.
- Nguyen, Thanh Binh,Ermolenko, Ludmila,Al-Mourabit, Ali
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- Two new mixed copper(ii)-dipeptide complexes of N, N -donor heterocycle ligands: Studies on their non-covalent DNA binding, chemical nuclease, antioxidant and anticancer activities
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Two novel mononuclear mixed ligand copper(ii) complexes, [Cu(Gly-l-val)(HPB)(H2O)]·ClO4·1.5H2O (1) and [Cu(Gly-l-val)(PBT)(H2O)]·ClO4 (2) (Gly-l-val = glycyl-l-valine, HPB = 2-(2′-pyridyl)benzimidazole, PBT = 2-(2′-pyridyl)benzothiazole), have been synthesized and characterized using various analytical and spectroscopic methods. The interactions of the complexes with DNA have been explored by viscometry, thermal denaturation, cyclic voltammetry (CV), agarose gel electrophoresis and spectroscopic means (UV absorption, circular dichroism (CD) and fluorimetry), as well as molecular docking techniques. These studies confirmed the mode of the complexes bound to calf thymus DNA (CT-DNA) through insertion with certain affinity (Kb = 3.211 × 105 M-1 for 1 and 4.734 × 104 M-1 for 2). In the fluorimetric experiments of thermodynamics (KSV = 1.145 × 104 M-1 for 1 and 2.634 × 103 M-1 for 2), the changes in enthalpy (ΔH > 0), entropy (ΔS > 0) and Gibbs free energy (ΔG ?OH as a reactive oxygen species. Furthermore, the molecular docking technique was applied to ascertain the mode of action for the complexes towards DNA. Moreover, superoxide dismutase (SOD) activity studies were performed using the photoreduction of nitroblue tetrazolium (NBT) under a non-enzymatic system and the antioxidant activities of 1 and 2 determined with IC50 values of 0.337 and 0.146 μM, respectively. The cytotoxicity of the Cu(ii) complexes against A549, HeLa, PC-3 tumor cell lines and NIH3T3 (non-tumor cell line) was studied by an MTT assay and it was found that 1 exhibited better cytotoxicity against A549 and PC-3 than 2 and the widely used drug cisplatin.
- Gan, Qian,Zhang, Chun-Lian,Wang, Bing-Feng,Xiong, Ya-Hong,Fu, Yin-Lian,Mao, Zong-Wan,Le, Xue-Yi
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- Mesoporous silica supported ytterbium as catalyst for synthesis of 1,2-disubstituted benzimidazoles and 2-substituted benzimidazoles
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The benzimidazole ring is an important pharmacophore in contemporary drug discovery. Thus, effort to identifying new compounds containing benzimidazole scaffolds have gained much attention in recent years. In the present study, MCM-41 type mesoporous silica with large pore (l-MSN) supported ytterbium was successfully prepared by wet impregnation method. Among rare earth metal salts, ytterbium triflate has already been widely investigated as a catalyst in organic synthesis but less toxic ytterbium oxide has yet to be explored. Relatively high abundance and low cost of ytterbium with respect to many catalytically active metals (e.g. Pd, Au, Ru, Ir, Pt) offer an opportunity to develop sustainable catalysts for organic conversions. The catalyst has been characterized by various techniques including nitrogen adsorption, FT-IR, TEM, SEM, EDX technique and elemental mapping. The obtained materials exhibit high surface area and a narrow distribution of mesoporosity. The catalytic performance of the Yb@l–MSNs was tested by synthesis of 1,2-disubstituted benzimidazoles and 2-substituted benzimidazoles through the coupling of aldehydes with o-phenylenediamine. The catalyst resulted in excellent yields in short reaction times and the reaction showed tolerance toward both electron-donating and electron-withdrawing functional groups at room temperature. A particularly interesting finding was the solvent selectivity of this reaction; namely, 1,2-disubstituted benzimidazoles generated as major product in water-ethanol, while the 2-substituted benzimidazoles was generated exclusively in non-polar solvents like toluene.
- Samanta, Partha Kumar,Banerjee, Rumeli,Richards, Ryan M.,Biswas, Papu
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- A comparative study of the optical and electroluminescent properties of EuIII complexes with TTA and 2-(2′-pyridyl)azoles: The crystal structure of [Eu(TTA)3(PBO)]
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Two EuIII mixed-ligand complexes, namely [Eu(TTA) 3(PBO)] and [Eu(TTA)3(PBT)] [TTA = 1,1,1-trifluoro-3-(2- thenoyl)acetonato, PBO = 2-(2′-pyridyl)-1,3-benzoxazole, and PBT = 2-(2′-pyridyl)-1,3-benzothiazole], have been synthesized. [Eu(TTA) 3(PBO)] has been structurally characterized by single-crystal X-ray diffraction analysis. The complex crystallizes in the monoclinic space group C2/c. The lattice parameters are a = 41.346(4), b = 10.0538(8), c = 20.3793(16) A, β = 110.922(2)°, Z = 8. The EuIII ion is eight-coordinate, with three bidentate TTA- anions and one bidentate N,O-chelated PBO molecule. A comparative study by UV and emission spectroscopy was carried out and electroluminescent properties of the related complexes [Eu(TTA)3(PBO)] and [Eu-(TTA)3(PBT)] are reported as well. Wiley-VCH Verlag GmbH & Co. KGaA, 2006.
- Gao, Li-Hua,Guan, Min,Wang, Ke-Zhi,Jin, Lin-Pei,Huang, Chun-Hui
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- Reaction intermediates of quinol oxidation in a photoactivatable system that mimics electron transfer in the cytochrome bc1 complex
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Current competing models for the two-electron oxidation of quinol (QH 2) at the cytochrome bc1 complex and related complexes impose distinct requirements for the reaction intermediate. At present, the intermediate species of the enzymatic oxidation process have not been observed or characterized, probably due to their transient nature. Here, we use a biomimetic oxidant, excited-state Ru(bpy)2(pbim)+ (bpy = 2,2′-dipyridyl, pbim = 2-(2-pyridyl)benzimidazolate) in an aprotic medium to probe the oxidation of the ubiquinol analogue, 2,3-dimethoxy-5-methyl-1,4- benzoquinol (UQH2-0), and the plastoquinol analogue, trimethyl-1,4-benzoquinol (TMQH2-0), using time-resolved and steady-state spectroscopic techniques. Despite its simplicity, this system qualitatively reproduces key features observed during ubiquinol oxidation by the mitochondrial cytochrome bc1 complex. Comparison of isotope-dependent activation properties in the native and synthetic systems as well as analysis of the time-resolved direct-detection electron paramagnetic resonance signals in the synthetic system allows us to conclude that (1) the initial and rate-limiting step in quinol oxidation, both in the biological and biomimetic systems, involves electron and proton transfer, probably via a proton-coupled electron-transfer mechanism, (2) a neutral semiquinone intermediate is formed in the biomimetic system, and (3) oxidation of the QH./QH2 couple for UQH2-0, but not TMQH 2-0, exhibits an unusual and unexpected primary deuterium kinetic isotope effect on its Arrhenius activation energy (ΔGTS), where ΔGTS for the protiated form is larger than that for the deuterated form. The same behavior is observed during steady-state turnover of the cyt bc1 complex using ubiquinol, but not plastoquinol, as a substrate, leading to the conclusion that similar chemical pathways are involved in both systems. The synthetic system is an unambiguous n = 1 electron acceptor, and it is thus inferred that sequential oxidation of ubiquinol (by two sequential n = 1 processes) is more rapid than a truly concerted (n = 2) oxidation in the cyt bc1 complex.
- Cape, Jonathan L.,Bowman, Michael K.,Kramer, David M.
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- The synthesis of azo compounds from nitro compounds using lead and triethylammonium formate
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Chemoselective synthesis of benzimidazoles in good yield was achieved with a variety of aldehydes in heterogeneous media. This efficient procedure has been developed for the condensation of ortho-phenylene-diamine with aldehydes by silica-supported thionyl chloride in dichloromethane at ambient temperature.
- Alloum, Abdelkrim Ben,Bougrin, Khalid,Soufiaoui, Mohamed
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- Single-component Eu3+-Tb3+-Gd3+-grafted polymer with ultra-high color rendering index white-light emission
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Through an approach of pre-coordination and following terpolymerization from vinyl-functionalized complex monomers [Ln(TTA)3(4-VB-PBI)] (Ln = Eu, 2; Ln = Tb, 3 and Ln = Gd, 4; HTTA = 2-thenoyltrifluoroacetonate; 4-VB-PBI = 1-(4-vinylbenzyl)-2-(pyridin-2-yl)-1H-benzo[d]imidazole) with methyl methacrylate, the first example of a single-component Eu2+-Tb3+-Gd3+-grafted polymer Poly(MMA-co-2-co-3-co-4) was obtained. Moreover, control of an optimal dye content for suppressing Tb3+ to Eu3+ energy transfer and exciton formation provides new perspectives for hetero-Ln3+-grafted polymers as featured in Poly(MMA-co-2-co-3-co-4) with color-tuning to direct white-light (Commission International De L'Eclairage coordinates of x = 0.322, y = 0.331; corrected color temperature of 5979 K; and color rendering index up to 94), including a highly luminous efficiency of 17.8%.
- Liu, Lin,Fu, Guorui,Li, Baoning,Lü, Xingqiang,Wong, Wai-Kwok,Jones, Richard A.
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- Photophysics of Three Pyridylbenzimidazoles in Solution
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Fluorescence decay time data are presented for the three benzimidazoles with pyridine substituted at the 2 position.The anomalous behavior of 2-(2'-pyridyl)benzimidazole in alcohols is explained in terms of the alcohol facilitating hydrogen transfer from the imidazole ring to the pyridine nitrogen atom.The rate constants for this process have been evaluated by studying the quenching of the fluorescence of 2-(2'-pyridyl)benzimidazole in cyclohexane by ethanol.
- Brown, Robert G.,Entwistle, Neil,Hepworth, John D.,Hodgson, Kevin W.,May, Bernadette
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- Synthesis and electron-transfer properties of benzimidazole-functionalized ruthenium complexes for highly efficient dye-sensitized solar cells
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Novel heteroleptic ruthenium complexes - RD1, RD5, RD10 and RD11 - with ligands based on benzimidazole were synthesized and characterized for application to dye-sensitized solar cells (DSSC); the remarkable performance of RD5-based DSSC is understood for its superior light-harvesting ability and slower charge-recombination kinetics.
- Huang, Wei-Kai,Cheng, Chi-Wen,Chang, Shu-Mei,Lee, Yuan-Pern,Diau, Eric Wei-Guang
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- Imidazolium chloride-catalyzed synthesis of benzimidazoles and 2-substituted benzimidazoles from o-phenylenediamines and DMF derivatives
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A facile, general, and economical synthesis of diversely functionalized benzimidazoles and 2-substituted benzimidazoles has been realized via the imidazolium chloride-catalyzed cyclization of o-phenylenediamines with DMF derivatives. This protocol shows a broad substrate scope for aliphatic, aromatic, and heteroaromatic amides. A series of benzimidazoles and 2-substituted benzimidazoles have been obtained in moderate to excellent yields.
- Gan, Zongjie,Tian, Qingqiang,Shang, Suqin,Luo, Wen,Dai, Zeshu,Wang, Huajun,Li, Dan,Wang, Xuetong,Yuan, Jianyong
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- Cu(I) complexes regulated by N-heterocyclic ligands: Syntheses, structures, fluorescence and electrochemical properties
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Three mononuclear Cu(I) complexes, namely, [Cu(2-PBO)(PPh3)2]·ClO4·2CH2Cl2 (1), [Cu(3-PBO)(PPh3)2(ClO4)]·CH2Cl2 (2) and [Cu(PBM)(PPh3)2]·ClO4 (3) (2-PBO = 2-(2′-Pyridyl)benzoxazole, 3-PBO = 2-(3′-Pyridyl)benzoxazole, PBM = 2-(2′-Pyridyl)benzimidazole, PPh3 = triphenylphosphine) have been synthesized and characterized by elemental analyses, IR, 1H NMR, 13C NMR, X-ray single crystal diffraction and thermal analysis. Photoluminescent investigation shows that complexes 1–3 exhibit distinct tunable light green (512 nm)-to-yellow (557 nm) photoluminescence by varying the N-heterocyclic ligands. Three complexes show intense 2-PBO-based yellow, 3-PBO-based light green and intense PBM-based bright green luminescence upon irradiation with a standard UV lamp (λex = 254 nm) at room temperature. Moreover, the electrochemical properties of 1–3 have been investigated by cyclic voltammetry. The results suggest the frontier molecular orbits and the HOMO-LUMO energy gaps of these cuprous complexes are effectively adjusted through the introduction of different N-heterocyclic ligands, thus achieving the selective luminescence of the cuprous complexes.
- Mao, Shanshan,Han, Xintong,Li, Chuang,Xu, Yuling,Shen, Kesheng,Shi, Xinkui,Wu, Huilu
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- Amide-imine conjugate involving gallic acid and naphthalene for nano-molar detection, enrichment and cancer cell imaging of La3+: Studies on the catalytic activity of the La3+complex
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A single crystal X-ray structurally characterized amide-imine conjugate (GAN) derived from gallic acid and naphthalene selectively recognizes La3+ ions via TURN ON fluorescence through ESIPT and CHEF mechanisms. GAN can detect as low as 23.93 × 10-9 M La3+ ions and image intracellular La3+ ions in live HeLa and SiHa cells under a fluorescence microscope in a time- and concentration dependent manner. The corresponding [La(iii)-GAN] complex is established as an efficient catalyst for the synthesis of benzimidazole derivatives from o-phenylenediamine and substituted benzaldehydes. Moreover, GAN is very useful for enrichment of La3+ in ethyl acetate medium. This journal is
- Shaikh, Ahad,Ghosh, Milan,Mukherjee, Pallabi,Ghosh, Avijit,Molla, Rostam Ali,Ta, Sabyasachi,Das, Debasis
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- Microwave-assisted synthesis of 2-(2-pyridyl)azoles. Study of their corrosion inhibiting properties
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(Chemical Equation Presented) An efficient and fast procedure for the synthesis of 2-(2-pyridyl)azoles is described using ionic liquids as catalysts under microwave irradiation. The X-ray crystallographic analyses for three of the four synthesized compounds are presented. Potentiodynamic polarization studies were carried out to analyze the electrochemical behavior of the compounds in corrosive acidic media. Of the four derivatives, one compound was detected to be an effective corrosion inhibitor prototype for oil refinery environments.
- Likhanova, Natalya V.,Veloz, M. Aurora,Hoepfl, Herbert,Matias, Diana J.,Reyes-Cruz, Victor E.,Olivares, Octavio,Martinez-Palou, Rafael
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- Synthesis and antiinflammatory activity of some 2-(substituted-pyridinyl)benzimidazoles
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A series of 2-(2-pyridinyl)benzimidazoles was synthesized and evaluated for antiinflammatory activity by the carrageenan-induced rat paw edema assay. Among several active derivatives, 2-(5-ethylpyridin-2-yl)benzimidazole was selected for further study. A comparison of this compound with phenylbutazone and tiaramide revealed that it possesses stronger activity in acute inflammatory models possibly with slightly less gastrointestinal irritation than both phenylbutazone and tiaramide.
- Tsukamoto,Yoshino,Kohno,Ohtaka,Kagaya,Ito
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- Antimicrobial evaluation of myricetin derivatives containing benzimidazole skeleton against plant pathogens
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A series of novel myricetin derivatives containing benzimidazole skeleton were constructed. The structure of compound 4g was further corroborated via X-ray single crystal diffractometer. The antimicrobial bioassays showed that all compounds exhibited potent inhibitory activities against Xanthomonas axonopodis pv. Citri (Xac), Ralstonia solanacearum (Rs) and Xanthomonas oryzae pv. Oryzae (Xoo) in vitro. Significantly, compound 4q showed the best inhibitory activities against Xoo, with the EC50 value of 8.2 μg/mL, which was better than thiodiazole copper (83.1 μg/mL) and bismerthiazol (60.1 μg/mL). In vivo experimental studies showed that compound 4q can treat rice bacterial leaf blight at 200 μg/mL, and the corresponding curative and protection efficiencies were 45.2 and 48.6%, respectively. Meanwhile, the antimicrobial mechanism of the compounds 4l and 4q were investigated through scanning electron microscopy (SEM). Studies showed that compounds 4l or 4q can cause deformation or rupture of Rs or Xoo cell membrane. These results indicated that novel benzimidazole-containing myricetin derivatives can be used as a potential antibacterial reagent.
- Chen, Mei,Tang, Xuemei,Liu, Tingting,Peng, Feng,Zhou, Qing,Luo, Hui,He, Ming,Xue, Wei
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- Electrocatalytic CO2 Reduction with a Half-Sandwich Cobalt Catalyst: Selectivity towards CO
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We present herein a Cp*Co(III)-half-sandwich catalyst system for electrocatalytic CO2 reduction in aqueous acetonitrile solution. In addition to an electron-donating Cp* ligand (Cp=pentamethylcyclopentadienyl), the catalyst featured a proton-responsive pyridyl-benzimidazole-based N,N-bidentate ligand. Owing to the presence of a relatively electron-rich Co center, the reduced Co(I)-state was made prone to activate the electrophilic carbon center of CO2. At the same time, the proton-responsive benzimidazole scaffold was susceptible to facilitate proton-transfer during the subsequent reduction of CO2. The above factors rendered the present catalyst active toward producing CO as the major product over the other potential 2e/2H+ reduced product HCOOH, in contrast to the only known similar half-sandwich CpCo(III)-based CO2-reduction catalysts which produced HCOOH selectively. The system exhibited a Faradaic efficiency (FE) of about 70percent while the overpotential for CO production was found to be 0.78 V, as determined by controlled-potential electrolysis.
- Kumar Pandey, Indresh,Kumar, Abhishek,Choudhury, Joyanta
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- Copper-catalyzed one-pot synthesis of benzimidazole derivatives
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A simple, efficient, and environmentally benign method has been developed for the synthesis of 2-substituted benzimidazoles through a one-pot reaction of phenylenediamines with ary1 aldehydes in excellent isolated yields under mild conditions using Cu(II) complex as the selective, recyclable, and heterogeneous catalyst at ambient temperature. The Cu(II) complex as a heterogeneous catalyst can be reused in further catalytic reactions, and it was found that its activity remained largely unchanged for eight successive runs. No metal-complex leaching was observed after the consecutive catalytic reactions. The salient features of this method include mild conditions, high yields, simple procedure, and good recovery and reusability of the heterogeneous catalyst.
- Sharghi, Hashem,Hosseini-Sarvari, Mona,Moeini, Fatemeh
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- Novel dye sensitizers of main chain polymeric metal complexes based on complexes of 2-(2′-pyridyl)benzimidazole derivative with Zn(II), Co(II): Synthesis, characterization, and photovoltaic performance for dye-sensitized solar cells
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In this paper, four novel D-π-A polymeric metal complex as dye sensitizers for dye-sensitized solar cell, which have Poly(p-phenylenevinylene) or carbazole derivative used as an electron donor, thiophene derivatives used as π-bridge and 2-(2′-pyridyl)benzimidazole derivative metal (Zn, Co) complex used as an electron acceptor (A) were synthesized and characterized. They have been determined and studied by FT-IR, TGA, DSC, GPC, elemental analysis, UV-vis absorption spectroscopy, photoluminescence spectroscopy, cyclic voltammetry, J-V curves and IPCE plots. The results show that four novel polymeric metal complex exhibited good photovoltaic property and thermal stability. The DSSC fabricated by P1, P2, P3 and P4 exhibit good device performance with a power conversion efficiency of up to 2.15, 2.27, 2.30 and 2.41 % (under simulated air mass 1.5 G irradiation) respectively, indicating the polymeric metal complexes are promising in the development of DSSC.
- Peng, Dahai,Zhang, Wei,Tang, Guipeng,Zhou, Jun,Hu, Jiaomei,Xie, Qiufang,Zhong, Chaofan
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- Silphox [POCl3-n(SiO2)n] as a new, efficient, and heterogeneous reagent for the synthesis of benzimidazole derivatives under microwave irradiation
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Silphox [POCl3-n(SiO2)n] efficiently catalyzes the condensation of benzene-1,2-diamine with mono and dicarboxylic acids under microwave irradiation to afford benzimidazole derivatives in high yields and short reaction times.
- Hasaninejad, Alireza,Niknam, Khodabakhsh,Zare, Abdolkarim,Farsimadan, Ehsan,Shekouhy, Mohsen
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- Concentrated solar radiation promoted unconventional greener approach: Solvent-free benign synthesis of functionalized benzimidazoles
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Renewable concentrated solar-radiation (CSR) offered a promising en route for the development of practical, highly efficient, scalable, catalyst free and solvent-free clean process leading to the synthesis of functionalized benzimidazoles. Developed protocol has a very good substrate scope, involves mild reaction conditions and products obtained in good to excellent yields. Method presented the observations in which light alone could affect the remarkable changes with more than 85% energy saving and 75% less reaction time in listed organic transformations.
- Harsh, Simran,Yusuf, Mohamad,Sharma, Rohit,Kumar, Yogesh,Kumar, Rupesh
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- Titanium, zirconium and vanadium complexes of 2-(benzimidazolyl, benzothiazolyl, and benzoxazolyl) pyridine as catalyst precursors for ethylene polymerization
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Dissymmetric chelating complexes of Ti, Zr and V with 2-(benzimidazolyl, benzothiazolyl, and benzoxazolyl) pyridine ligands were synthesized and characterized. After activation with methylalumoxane (MAO) in solution, these complexes could be applied as ethylene polymerization catalysts. Their activities depend on the metal and the substituents at the pyridine ring and the heterocycle. Structure-property-relationship studies revealed that the titanium and vanadium catalyst systems showed higher polymerization activities than the zirconium analogues. The benzoxazolyl moiety containing vanadium complex 29, with a methyl substituent in the 6-membered ring in meta position to the nitrogen atom in the 5-membered ring, and an unsubstituted pyridine ring showed the highest activity (1154.8 kg PE/mol cat h). The produced polyethylenes exhibited high molecular weights and broad molecular weight distributions. Obviously different active sites are generated in the course of these polymerization reactions.
- Elagab, Hamdi Ali,Alt, Helmut G.
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- Structure-activity relationships in cytotoxic AuI/Au III complexes derived from 2-(2′-pyridyl)benzimidazole
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Gold(I) and gold(III) complexes derived from 2-(2′-pyridyl) benzimidazole (pbiH) were proven to be a promising class of in vitro antitumor agents against A2780 human ovarian cancer cells. In this paper, a comparative electrochemical, UV-vis absorption, and emission spectroscopic investigation is reported on pbiH, the two mononuclear AuIII complexes [(pbi)AuX 2] (X = Cl (1), AcO (2)), the four mononuclear AuI derivatives [(pbiH)AuCl] (3), [(pbiH)Au(PPh3)]PF6 ((4 +)(PF6-)), [(pbi)Au(PPh3)] (5), and [(pbi)Au(TPA)] (6), the three mixed-valence AuIII/AuI complexes [(μ-pbi)Au2Cl3] (7), [(Ph3P) Au(μ-pbi)AuX2]PF6 (X = Cl ((8+)(PF 6-)), AcO ((9+)(PF6-))), and the binuclear AuI-AuI compound [(μ-pbi)Au 2(PPh3)2]PF6 ((10 +)(PF6-)). All complexes feature irreversible reduction processes related to the AuIII/AuI or Au I/Au0 processes and peculiar luminescent emission at about 360-370 nm in CH2Cl2, with quantum yields that are remarkably lower ((0.7-14.5) × 10-2) in comparison to that determined for the free pbiH ligand (31.5 × 10-2) in the same solvent. The spectroscopic and electrochemical properties of all complexes were interpreted on the grounds of time-dependent PBE0/DFT calculations carried out both in the gas phase and in CH2Cl2 implicitly considered within the IEF-PCM SCRF approach. The electronic structure of the complexes, and in particular the energy and composition of the Kohn-Sham LUMOs, can be related to the antiproliferative properties against the A2780 ovarian carcinoma cell line, providing sound quantitative structure-activity relationships and shedding a light on the role played by the global charge and nature of ancillary ligands in the effectiveness of Au-based antitumor drugs.
- Maiore, Laura,Aragoni, Maria Carla,Deiana, Carlo,Cinellu, Maria Agostina,Isaia, Francesco,Lippolis, Vito,Pintus, Anna,Serratrice, Maria,Arca, Massimiliano
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- Photoluminescence and electrochemical studies of tetranuclear ruthenium(II) polypyridyl complexes of benzimidazolyl functionalised pyrenylcalix[4]resorcinarene
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We report the hitherto unreported pyrene footed calix[4]resorcinarene (P1) supramolecular assembly and its tetranuclear Ru(II) polypyridyl complexes, [{Ru(phen)2}4(L)](ClO4)8 (CP1), [{Ru(bpy)2}4(L)](ClO4)8 (CP2), and [{Ru(P2)2}4(L)](ClO4)8 (CP3) [where, L = 2,8,14,20-tetra(pyren-1-yl)-5,11,17,23-tetrakis((2-(pyridin-2-yl)-1H-benzimidazol-1-yl)methyl)-4,6,10,12,16,18,22,24-octahydroxy-calix[4]resorcinarene and P2 = 2-(pyridin-2-yl)-1H-benzimidazole]. The single crystal structure of 2,8,14,20-tetra(pyren-1-yl)-4,6,10,12,16,18,22,24-octahydroxycalix[4]-resorcinarene (P1) possesses all cis configuration and a boat like conformation with pyrene rings occupying the axial positions. The tetranuclear complexes, CP1, CP2 and CP3, show decreasing energy of 3MLCT luminescence at 298 K but the intensity is increased at 77 K in frozen acetonitrile due to lowering of energy gap between π* of the ligand and the d orbital of ruthenium metal ion. The luminescence quantum yield has also been increased considerably in all the complexes when the temperature is decreased from 298 K to 77 K due to the lowering of nonradiative decay pathways. The complexes exhibit a single exponential decay profile in acetonitrile at 298 K. The cyclic voltammograms of the complexes show simultaneous four single electron quasireversible redox processes.
- Louis, Ligimol,Alexander,Kumar, D. Suresh,Senthan, S. Amudhan,Viveke, A. Arun
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- [Diaquo{bis(p-hydroxybenzoato-κ1O1)}(1-methylimidazole- κ1N1)}copper(II)]: Synthesis, crystal structure, catalytic activity and DFT study
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Metal-organic hybrid complexes often exhibit large surface area, pore volume, fascinating structures and potential applications including catalytic applications. Hence a new metal-organic hybrid complex [Diaquo{bis(p-hydroxybenzoato-κ1O1)}(1-methylimidazole- κ1N1)}copper(II)] was synthesized using conventional method. Physico-chemical characterization of the complex was performed with FTIR spectroscopy, single crystal X-ray diffraction, TGA, EPR and FESEM. Single crystal X-ray diffraction study suggests it to be three dimensional with space group P212121 (orthorhombic). The crystal achieves its three-dimensional structure and stability through extensive intermolecular hydrogen bonding. Hirshfeld surface analysis, catalytic activity and DFT study of the complex was also performed. The synthesized complex acts as good catalyst in benzimidazole synthesis with good recyclability as catalyst up to 5th run.
- Brahman, Dhiraj,Chhetri, Sailesh,Kamath, Amarjit,McArdle, Patrick,Sinha, Biswajit
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- s-Tetrazine-functionalized hyper-crosslinked polymers for efficient photocatalytic synthesis of benzimidazoles
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Developing green-safe, efficient and recyclable catalysts is crucial for the chemical industry. So far, organic photocatalysis has been proved to be an environmentally friendly and energy-efficient synthetic technology compared with traditional metal catalysis. As a versatile catalytic platform, hyper-crosslinked polymers (HCPs) with large surface area and high stability are easily prepared. In this report, we successfully constructed two porous HCP photocatalysts (TZ-HCPs) featurings-tetrazine units and surface areas larger than 700 m2g?1through Friedel-Crafts alkylation reactions. The rational energy-band structures and coexisting micro- and mesopores endow TZ-HCPs with excellent activities to realize the green synthesis of benzimidazoles (28 examples, up to 99% yield, 0.5-4.0 h) in ethanol. Furthermore, at least 21 iterative catalytic runs mediated by TZ-HCP1D were performed efficiently, with 96-99% yield. This study of TZ-HCPs sheds light on the wide-ranging prospects of application of HCPs as metal-free and green photocatalysts for the preparation of fine chemicals.
- An, Wan-Kai,Zheng, Shi-Jia,Zhang, Hui-Xing,Shang, Tian-Tian,Wang, He-Rui,Xu, Xiao-Jing,Jin, Qiu,Qin, Yuchen,Ren, Yunlai,Jiang, Song,Xu, Cui-Lian,Hou, Mao-Song,Pan, Zhenliang
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supporting information
p. 1292 - 1299
(2021/02/26)
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- Benzotrithiophene and triphenylamine based covalent organic frameworks as heterogeneous photocatalysts for benzimidazole synthesis
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Metal-free covalent organic frameworks (COFs) as visible-light active and recyclable photocatalysts afford an eco-friendly and sustainable option to classical photosensitizers, which usually require noble metals (iridium, ruthenium, rhodium, etc.) to produce photocatalytic activity. Most classical small molecule photosensitizers have poor recyclability with certain limitations. As a result, it is of great significance to develop a metal-free and easily recyclable COF photocatalyst. In this study, we designed and synthesized a new type of COF photocatalyst (BTT-TPA-COF) in which benzotrithiophene and triphenylamine units are alternately connected. It has high specific surface area, permanent porosity and good stability. In addition, this design strategy can effectively adjust the band gap, energy level and photoelectric performance of BTT-TPA-COF. As a metal-free photocatalyst, BTT-TPA-COF exhibits high-efficiency photocatalytic activity, excellent substrate tolerance and excellent recyclability for the synthesis of 2-arylbenzimidazole compounds. This research not only puts forward a design strategy for high-efficiency photocatalysts, but also broadens the application range of COF materials in photocatalytic organic reactions.
- Chen, Ying,Huo, Jianqiang,Luo, Bingcai,Zhang, Yubao
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- Visible-light-mediated organoboron-catalysed metal-free dehydrogenation of N-heterocycles using molecular oxygen
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The surge of photocatalytic transformation not only provides unprecedented synthetic methods, but also triggers the enthusiasm for more sustainable photocatalysts. On the other hand, oxygen is an ideal oxidant in terms of atom economy and environmental friendliness. However, the poor reactivity of oxygen at the ground state makes its utilization challenging. Herein, a visible-light-induced oxidative dehydrogenative process is disclosed, which uses an organoboron compound as the photocatalyst and molecular oxygen as the sole oxidant.Viathis approach, an array of N-heterocycles have been accessed under metal-free mild conditions, in good to excellent yields.
- Wei, Lanfeng,Wei, Yu,Xu, Liang,Zhang, Jinli
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supporting information
p. 4446 - 4450
(2021/06/30)
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- Method for preparing N - heterocyclic ring through visible light mediated dehydrogenation
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The invention discloses a method for preparing N - heterocyclic rings through visible light mediated dehydrogenation, and the reaction can be carried out under the conditions of room temperature and visible light without heating. The novel tetra-coordination N-N - diaryl chelating borate compound serves as a photocatalyst, so that the use of a noble metal photocatalyst is avoided, precious metal residue in the reaction product can be reduced as much as possible, and the method is more suitable for synthesizing bioactive molecules.
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Paragraph 0166-0171
(2021/10/02)
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- Ionic liquid-immobilized hybrid nanomaterial: an efficient catalyst in the synthesis of benzimidazoles and benzothiazoles via anomeric-based oxidation
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Abstract: In this study, a novel ionic liquid immobilized on silica-coated cobalt-ferrite magnetic nanoparticles. This novel hybrid nanostructure (CoFe2O4@SiO2@PAF-IL) was characterized by various microscopic and spectroscopic techniques including Fourier transformation infrared spectroscopy (FT–IR), X-ray powder diffraction (XRD), field emission scanning electron microscopy (SEM), the electron-dispersive X-ray spectroscopy (EDS), vibrating sample magnetometer (VSM), and thermogravimetric analysis (TGA/DTG). The catalytic activity of prepared nanomaterial was considered in the synthesis of the benzothiazole and benzimidazole derivatives. This method has several advantages such as good to excellent yields, short reaction times, solvent-free and environmentally-benign conditions, and simple work-up. Besides, nanocatalyst can be easily separated from the reaction mixture with the external magnetic field and reused several times without any loss of its catalytic activity. Graphic abstract: [Figure not available: see fulltext.].
- Bodaghifard, Mohammad Ali,Shafi, Saeideh
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p. 677 - 687
(2020/09/18)
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- A Novel Synthesis of 2-Arylbenzimidazole and 2-Arylbenzothiazole Derivatives by MnO2/MOF-199
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The main objective of this research is to develop efficient and environmentally benign heterogeneous catalysts for synthesis of 2-arylbenzimidazole and 2-arylbenzothiazoles derivatives by MnO2/MOF-199. For this purpose, a heterogeneous MnO2/MOF-199 catalyst was prepared by the solvothermal method, and the prepared catalyst was characterised by various techniques such as X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), BET, IR, thermogravimetric-differential thermogravimetric (TG-DTG), and temperature-programmed desorption with ammonia (NH3-TPD) analysis. The solid catalyst, with a MnO2/MOF-199 loading of 9 %, demonstrated a high catalytic activity in the synthesis of 1,2-arylbenzimidazole and 1,2-arylbenzothiazole derivatives and the catalyst could be reused for at least 5 cycles under mild conditions.
- Amouhadi, Elham,Fazaeli, Razieh,Aliyan, Hamid
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p. 495 - 502
(2021/02/09)
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- A one-step synthesis of substituted benzo- and pyridine-fused 1H-imidazoles
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Substituted benzimidazoles and pyrimidazoles are an important group of heterocyclic aromatic organic compounds in the field of medicinal chemistry. A one-step microwave accelerated synthesis of substituted benzo- and pyridine-fused 1H-imidazoles has been described. Mechanistically, the reaction proceeds by reacting substituted 2-fluoronitrobenzene and substituted arylamine through the formation of N-hydroxy intermediate, which at higher temperature cleaves to afford the desired product. This approach achieved reductions in reaction times, higher yields, cleaner reactions than the previously described synthetic processes.
- Bhatt, Ashish,Kant, Ravi,Kumar, Sonu,Reddy, Yella,Sarmah, Manash P.
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- H2 Activation with Co Nanoparticles Encapsulated in N-Doped Carbon Nanotubes for Green Synthesis of Benzimidazoles
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Co nanoparticles (NPs) encapsulated in N-doped carbon nanotubes (Co@NC900) are systematically investigated as a potential alternative to precious Pt-group catalysts for hydrogenative heterocyclization reactions. Co@NC900 can efficiently catalyze hydrogenative coupling of 2-nitroaniline to benzaldehyde for synthesis of 2-phenyl-1H-benzo[d]imidazole with >99 % yield at ambient temperature in one step. The robust Co@NC900 catalyst can be easily recovered by an external magnetic field after the reaction and readily recycled for at least six times without any evident decrease in activity. Kinetic experiments indicate that Co@NC900-promoted hydrogenation is the rate-determining step with a total apparent activation energy of 41±1 kJ mol?1. Theoretical investigations further reveal that Co@NC900 can activate both H2 and the nitro group of 2-nitroaniline. The observed energy barrier for H2 dissociation is only 2.70 eV in the rate-determining step, owing to the presence of confined Co NPs in Co@NC900. Potential industrial application of the earth-abundant and non-noble transition metal catalysts is also explored for green and efficient synthesis of heterocyclic compounds.
- Lin, Chuncheng,Wan, Weihao,Wei, Xueting,Chen, Jinzhu
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p. 709 - 720
(2020/11/30)
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- Functional POM-catalyst for selective oxidative dehydrogenative couplings under aerobic conditions
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Development of selective and efficient reusable catalytic systems for sustainable chemical production under benign conditions is attractive and received much attention. Herein, we report a rod-shaped octadecyl trimethylammonium functionalized Keggin-type polyoxometalate [PMO12O40] hybrids (OTA-POM) as an efficient heterogeneous catalyst for selective oxidative dehydrogenative couplings under aerobic conditions without any additive or external base. The catalyst recovery and subsequent five successive recyclability studies of hybrid POM confirms the heterogeneous nature of present catalytic system.
- Samaraj, Elavarasan,Balaraman, Ekambaram,Manickam, Sasidharan
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- A heterogeneous catalytic strategy for facile production of benzimidazoles and quinoxalines from primary amines using the Al-MCM-41 catalyst
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This study reports a straightforward heterogeneous catalytic (Al-MCM-41) approach to synthesize nitrogen heterocycle moieties from primary amines under solvent-free conditions. The Al-MCM-41 catalyst was prepared using a hydrothermal method and characterized by various analytical techniques. The probability and limitations of the catalytic methodology were presented with various substrates. The catalytic method grants an attractive route to a wide variety of benzimidazole and quinoxaline moieties with good to excellent yields. The gram scale reaction and reusability (up to five cycles) of the Al-MCM-41 catalyst would greatly benefit industrial applications. This journal is
- Vasu, Amrutham,Naresh, Mameda,Krishna Sai, Gajula,Divya Rohini, Yennamaneni,Murali, Boosa,Ramulamma, Madasu,Ramunaidu, Addipilli,Narender, Nama
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p. 9439 - 9446
(2021/12/09)
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- Preparation method of 2-substituted benzimidazole compound
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The invention discloses a preparation method of a 2-substituted benzimidazole compound, and belongs to the field of synthesis of benzimidazole compounds. The 2-substituted benzimidazole compound is synthesized in an organic solvent by taking an o-nitroaniline compound, aromatic aldehyde, o-dinitrobenzene and aromatic aldehyde as raw materials and taking Co particles wrapped by a nitrogen-doped carbon material as a catalyst. According to the method, the 2-substituted benzimidazole compound can be prepared at room temperature, the reaction conditions are mild, the yield is as high as 95%, the selectivity is as high as 99%, and the method is economical, environmentally friendly and wide in substrate applicability. The used catalyst is easy to prepare, low in cost and good in reusability, canbe separated by utilizing magnetism, and is convenient to recover, so that the method has a relatively strong industrial application prospect.
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Paragraph 0084-0088
(2021/02/20)
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- Benzimidazole compound with endothelial lipase inhibition effect and application of benzimidazole compound
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The invention discloses a benzimidazole compound with an endothelial lipase inhibition effect and application of the benzimidazole compound, and belongs to the technical field of medicines. The benzimidazole compound has an excellent inhibition effect on endothelial lipase, can effectively treating atherosclerosis and sequelae thereof, such as coronary heart disease, and also promotes treatment onmetabolic syndrome and sequelae thereof, such as diabetes. The benzimidazole compound provided by the invention has good solubility in an aqueous medium, also has good biological activity and metabolic stability, and shows advantages in the aspect of serum stability.
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Paragraph 0097-0102
(2020/12/09)
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- Transforming Oxadiazolines through Nitrene Intermediates by Energy Transfer Catalysis: Access to Sulfoximines and Benzimidazoles
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Subtle differences in reaction conditions facilitated unprecedented photocatalytic reactions of oxadiazolines by energy transfer catalysis. A set of compounds, sulfoximines and benzimidazoles, were ingeniously prepared from oxadiazolines via nitrene intermediates by photocatalytic N-O/C-N bond cleavages. The synthesis of sulfoximines was realized through intermolecular N-S bond formation between nitrene intermediates and sulfoxides, whereas benzimidazoles were obtained via intramolecular aromatic substitution of the nitrene to the tethered aryl substituent.
- Park, Do Dam,Min, Kwan Hong,Kang, Jihee,Hwang, Ho Seong,Soni, Vineet Kumar,Cho, Cheon-Gyu,Cho, Eun Jin
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supporting information
p. 1130 - 1134
(2020/02/15)
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- Direct synthesis of 2-substituted benzimidazoles: Via dehydrogenative coupling of aromatic-diamine and primary alcohol catalyzed by a Co complex
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A Co(ii) complex with a stable structure was designed and synthesized with quinalic acid and Co (OAc)2·4H2O. The single crystal structure of the complex was characterized by X-ray diffraction. A dehydrogenative coupling of aromatic diamines and primary alcohols was developed by using the Co(ii) complex as the catalyst to synthesize 2-substituted benzimidazole. A series of 2-substituted benzimidazoles were obtained with good to excellent yields under mild reaction conditions. In addition, a compound with inhibitory Parkinson's activity was synthesized on a gram-scale by using this method. Finally, the reaction mechanism was proposed and the energy changes in the reaction process were simulated by density functional theory (DFT).
- Zuo, Minghui,Guo, Weihao,Pang, Yucheng,Guo, Rui,Hou, Chuanfu,Sun, Shouneng,Wu, Hongfeng,Sun, Zhizhong,Chu, Wenyi
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p. 14490 - 14495
(2020/10/03)
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- Nickel catalysed construction of benzazoles: Via hydrogen atom transfer reactions
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Herein we report a homogeneous, phosphine free, inexpensive nickel catalyst that forms a wide variety of benzazoles from alcohol and diamines by a reaction sequence of alcohol oxidation, imine formation, ring cyclization and dehydrogenative aromatization. A reversible azo/hydrazo couple, that is part of the ligand architecture steers both the alcohol oxidation and dehydrogenation of the annulated amine under fairly mild reaction conditions. Interestingly, both the alcohol oxidation and amine dehydrogenation steps are directly mediated by hydrogen atom transfer (HAT), which is greatly facilitated by the reduced ligand backbone. The kH/kD for the amine dehydrogenation step, measured at 60 °C is 5.9, fully consistent with HAT as the rate determining factor during this step. This is a unique scenario where two consecutive oxidation steps towards benzazole formation undergo HAT, which has been substantiated via kinetic studies, KIE determination and intermediate isolation. This journal is
- Adhikari, Debashis,Bains, Amreen K.,Dey, Dhananjay,Kundu, Abhishek,Yadav, Sudha
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p. 6495 - 6500
(2020/11/13)
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- Solvent-Free N-Alkylation and Dehydrogenative Coupling Catalyzed by a Highly Active Pincer-Nickel Complex
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The synthesis and characterization of a pincer-nickel complex of the type (iPr2NNN)NiCl2(CH3CN) is reported here. We have demonstrated the utility of this pincer-nickel complex (0.02 and 0.002 mol %) for the catalytic N-alkylation of amines using various alcohols. Under solvent-free conditions, while the highest yield (ca. 90%) was obtained for the alkylation of 2-aminopyridine with naphthyl-1-methanol, excellent turnovers (34000 TONs) were observed for the alkylation of 2-aminopyridine with 4-methoxybenzyl alcohol. To demonstrate the synthetic utility of these systems, high-yield reactions (up to 98%) have been probed for representative substrates with a higher loading of the pincer-nickel catalyst (4 mol %). DFT studies indicate that while β-hydride elimination is the RDS for alcohol dehydrogenation, the N-alkylated product can be formed either via hydrogenation with a rate-determining σ-bond metathesis or by alcoholysis that has imine insertion as the RDS. All of the corresponding resting states have been observed by HRMS (ESI) analysis. The labeling experiments are also complementary to DFT studies and show evidence for the involvement of the benzylic C-H bond in the RDS with a kCHH/kCHD value of about 2.5. This method has been applied to accomplish efficient (2000 TONs) dehydrogenative coupling leading to various benzimidazoles.
- Arora, Vinay,Dutta, Moumita,Das, Kanu,Das, Babulal,Srivastava, Hemant Kumar,Srivastava, Hemant Kumar,Kumar, Akshai,Kumar, Akshai
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p. 2162 - 2176
(2020/06/05)
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- Synthesis of pyridinyl-benzo[d]imidazole/pyridinyl-benzo[d]thiazole derivatives and their yeast glucose uptake activity in vitro
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Background: Diabetes is the primary cause of fatality and disability all over the world, in recent past, we have reported various classes of compounds as anti-glycating agents and we have also reported benzimidazole and benzothiazole derivatives as a potential class of anti-glycating agents. This encouraged us to evaluate the pyridinyl benzimidazole/pyridinyl benzothiazole derivatives 1-27 for yeast glucose uptake activity. Methods: In the present study, an equimolar mixture of pyridine carboxaldehyde derivatives (1 mmol) and sodium metabisulphite (1 mmol) in DMF (10 mL) was stirred for 10 to 15 min, followed by addition of o-phenylene diamine/2-aminothiophenol (1 mmol) into it and refluxed for 3 h. The progress of the reaction was monitored by TLC. After completion, the reaction mixture was poured into crushed ice. Precipitates were formed which were collected by filtration to produce compounds 1-27 in good yields. Recrystallization from methanol yielded pure crystals. Results: Our present study showed that all compounds showed a varying degree of yeast glucose uptake activity in the range IC50 = 36.43-272.20 μM, compared to standard metronidazole (IC50 = 41.86 ± 0.09 μM). Compounds 5 (IC50 = 38.14 ± 0.17 μM), 6 (IC50 = 40.23 ± 0.20 μM), and 7 (IC50 = 36.43 ± 0.02 μM) showed an excellent yeast glucose uptake activity better than the standard. Conclusion: Pyridinyl benzimidazole/pyridinyl benzothiazole derivatives 1-27 were synthesized, structurally characterized, and evaluated for in vitro yeast glucose uptake activity. Compounds 5 (IC50 = 38.14 ± 0.17 μM), 6 (IC50 = 40.23 ± 0.20 μM), and 7 (IC50 = 36.43 ± 0.02 μM) demonstrated potent yeast glucose uptake activity as compared to standard metronidazole (IC50 = 41.86 ± 0.09 μM). This study identified a number of potential lead molecules which can be helpful in lowering the blood glucose level in hyperglycemia.
- Khan, Momin,Ahmad, Riaz,Rehman, Gauhar,Gul, Naeem,Shah, Sana,Salar, Uzma,Perveen, Shahnaz,Khan, Khalid Mohammed
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p. 984 - 993
(2019/10/28)
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- Visible-light-induced condensation cyclization to synthesize benzimidazoles using fluorescein as a photocatalyst
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A mild strategy for visible-light-induced synthesis of benzimidazoles was developed using aromatic aldehydes and o-phenylenediamines as substrates. The use of an organic dye, fluorescein, as an innoxious photocatalyst provided a mild and inexpensive catalytic system to synthesize a series of benzimidazoles in moderate to excellent yields. It was originally applied to this system to obtain benzimidazoles. Besides, the catalytic system does not require an additional oxidant or metal which was good for the environment.
- Li, Zhuofei,Song, He,Guo, Rui,Zuo, Minghui,Hou, Chuanfu,Sun, Shouneng,He, Xin,Sun, Zhizhong,Chu, Wenyi
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p. 3602 - 3605
(2019/07/09)
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- NOVEL ONE-POT HOMOGENEOUS PROCESS FOR THE LARGE SCALE MANUFACTURE OF 2-SUBSTITUTED BENZIMIDAZOLES
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2-substituted benzimidazoles and methods of preparing the same are disclosed. The compositions may include a compound or salt thereof, an acid, and a polar aprotic solvent. The compositions may be used to inhibit corrosion of a metal surface in contact with an aqueous system, and provide enhanced protection against corrosion of metals in the aqueous system.
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Paragraph 0155; 0156
(2019/05/24)
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- Dendritic iridium complex electroluminescent material capable of solution processing and synthetic method thereof
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The invention discloses a dendritic iridium complex electroluminescent material capable of solution processing and a synthetic method thereof. The molecular structure consists of two parts, one part is an iridium complex with room temperature phosphorescence property as a luminescent core, the other part is a racial with high triplet state energy level as a peripheral branch radial, and the two parts are connected through a non-conjugated radical. The molecule is of the structure as shown in the specification, wherein C1 to C3 are ionic dendritic iridium complexes, and C4 to C6 are neutral dendritic iridium complexes of similar structure. R1 and R2 are high triplet state energy level radicals with non-conjugated radical ends. The problems of synthesis, purification, device preparation technology and cost, existing in wet process preparation devices, of iridium complex materials can be solved.
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Paragraph 0084-0091
(2019/07/04)
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- Development of titania-supported iridium catalysts with excellent low-temperature activities for the synthesis of benzimidazoles via hydrogen transfer
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Titania-supported iridium catalysts which enable the synthesis of benzimidazoles from 2-nitroaniline and primary alcohols under mild conditions have been developed. The iridium catalysts supported on {010}/{101}-faceted anatase (PA-135-3.5) showed the excellent activity in spite of their moderate surface areas, while there is a positive correlation between BET surface area and the activity of iridium catalysts. TEM analysis revealed the formation of small iridium nanoparticles (mean diameter; 1.0 nm) on PA-135-3.5, which would be one reason for the excellent catalytic activity. According to the XPS study, relatively high-valent iridium species would be responsible for the catalysis. Various primary alcohols bearing electron-withdrawing or electron-donating groups were applicable. The removal of the solid catalyst by the hot filtration completely stopped further progress of the reaction, indicating that the catalyst acted heterogeneously. The catalysts could be recycled, and there was no leaching of iridium species into the solution.
- Fukutake, Tatsuhiro,Wada, Kenji,Yu, Han,Hosokawa, Saburo,Feng, Qi
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- A benzimidazole and synthetic method of derivative thereof (by machine translation)
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The present invention provides a benzimidazole and its derivative synthesis method, the method through the imidazole chloride catalyzed O-phenylenediamine cyclized, realizes the multi-functional chain dibasic and imidazole and 2 - substituted benzimidazole synthesis, method is simple and economic, and the practicability is strong. This invention does not have any other catalyst or additive, synthetic method has good functional group tolerance and excellent yield and purity, reaction time is short, and does not need the harsh reaction conditions, is suitable for industrial production. (by machine translation)
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Paragraph 0045; 0047; 0052; 0053
(2019/02/10)
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- Sulfonated carbon-encapsulated iron nanoparticles as an efficient magnetic nanocatalyst for highly selective synthesis of benzimidazoles
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Surface functionalized carbon-encapsulated iron nanoparticles (CEINs) were found to be a magnetic nanocatalyst for the efficient and highly selective synthesis of benzimidazoles. CEINs were covalently decorated with carboxyl or sulfonyl groups and their catalytic activity was examined. Carboxyl-modified CEINs were obtained via the radical or oxidative treatment, whilst the sulfonated CEINs were obtained using the one-step diazotization approach with sulfanilic acid and isoamyl nitrite. The content of surface acidic groups varied between the obtained materials and was found to be the highest for sulfonyl-modified CEINs. CEINs functionalized with sulfonyl groups were the most efficient and the most selective nanocatalyst for the synthesis of benzimidazoles. Various benzimidazoles were obtained in very high yields (92.5-97.0%). Both metallocene, aliphatic, heterocyclic and aromatic aldehydes substituted with different functional groups were subjected to the synthesis process. The reaction proceeded in a short time, which varied from 25 min to 65 min depending on the aldehyde used. Additionally, the mechanism of the studied catalytic condensation by applying sulfonated CEINs as the catalyst was discussed. Importantly, the developed magnetic nanocatalysts could be easily separated from the reaction mixture using a permanent magnet. The nanocatalysts can be used up to six reaction cycles without any significant loss of their catalytic activity. This work opens up new ways for very efficient and simple synthesis of benzimidazoles-an important class of organic compounds for various biomedical applications.
- Kasprzak, Artur,Bystrzejewski, Micha?,Poplawska, Magdalena
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p. 6314 - 6322
(2018/05/23)
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- Controlled Single and Double Iodofluorination of Alkynes with DIH- and HF-Based Reagents
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A novel protocol for the regio- and stereoselective iodofluorination of internal and terminal alkynes using 1,3-diiodo-5,5,-dimethylhydantoin and HF-based reagents is disclosed. This approach is used to prepare a fluorinated tamoxifen derivative in two steps from commercially available starting materials. A facile method enabling controlled regioselective double iodofluorination of terminal alkynes is also presented.
- Pfeifer, Lukas,Gouverneur, Véronique
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supporting information
p. 1576 - 1579
(2018/03/23)
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- Copper-catalysed synthesis of 3,5-disubstituted isoxazoles enabled by pyridinyl benzimidazol (PBI) as a bidentate N-chelating ligand under mild conditions
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In this paper, we introduced pyridinyl benzimidazol (PBI) as an easy-to-handle and bidentate N-chelating ligand that promote clean synthesis of 3,5-disubstituted isoxazoles in the presence of copper acetate as catalyst. This catalytic approach initiates with the hydroxyamination of aldehydes followed by chlorination and then generation of nitrile oxide which subsequently undergoes click-type [3?+?2]-dipolar cycloaddition with alkynes to give isoxazoles. This method provides an alternative green process to construct isoxazole derivatives.
- Khalifeh, Reza,Shahriarpour, Fatemeh,Sharghi, Hashem,Aberi, Mahdi
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p. 813 - 821
(2018/03/01)
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- Chloromethylated polystyrene immobilized ruthenium complex of 2-(2-pyridyl)benzimidazole catalyst for the synthesis of bioactive disubstituted ureas by carbonylation reaction
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Polymer supported transition metal complex catalysts have numerous applications as heterogeneous catalysts due to their ease of synthesis and commercial availability. Ru-Py-Merf was synthesized by anchoring 2-(2-pyridyl)benzimidazole to the polymer matrix, followed by loading of ruthenium salt. This Ru-Py-Merf material was thoroughly characterized by FTIR spectroscopy, UV-vis absorption spectroscopy, FE-SEM analysis, EDAX analysis, CHN analysis, AAS spectroscopy and TGA. Ru-Py-Merf showed excellent catalytic activity in the synthesis of symmetric and asymmetric disubstituted ureas by reductive carbonylation of nitrobenzenes and anilines. The as-synthesized Ru-Py-Merf catalyst is entirely heterogeneous in nature, thermally stable and can be easily reused up to six times.
- Dey, Tusar Kanto,Ghosh, Kajari,Basu, Priyanka,Molla, Rostam Ali,Islam, Sk. Manirul
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p. 9168 - 9176
(2018/06/08)
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- Synthesis of benzimidazoles by Cul-catalyzed three-component reaction of 2-haloaniline, ammonia and aldehyde in water
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An efficient copper-catalyzed three-component reaction of 2-haloaniline, ammonia and aldehyde for the synthesis of benzimidazoles with 1,10-phenanthroline as the ligand has been developed. A variety of substituted benzimidazole derivatives can be obtained in yields up to 95%.
- Ke, Fang,Zhang, Peng,Lin, Chen,Lin, Xiaoyan,Xu, Jianhua,Zhou, Xiangge
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supporting information
p. 8090 - 8094
(2018/11/23)
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- Microwave-Assisted Nickel-Catalyzed Synthesis of Benzimidazoles: Ammonia as a Cheap and Nontoxic Nitrogen Source
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An efficient and convenient Ni-catalyzed C-N bond formation for the synthesis of various benzimidazoles from various 2-haloanilines, aldehydes, and ammonia in a concise manner is reported. This protocol uses commercially available, nonhazardous, clean ammonia as a reaction partner instead of other nitrogen sources. Benzimidazoles, as the sole products, were obtained in high to excellent yields (up to 95%).
- Ke, Fang,Zhang, Peng,Xu, Yiwen,Lin, Xiaoyan,Lin, Jin,Lin, Chen,Xu, Jianhua
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supporting information
p. 2722 - 2726
(2018/12/14)
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- I2/TBHP promoted oxidative C–N bond formation at room temperature: Divergent access of 2-substituted benzimidazoles involving ring distortion
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A new ‘one pot’ tandem synthesis of 2-substituted benzimidazoles has been developed from 2-aminobenzyl alcohol/2-aminobenzamide and different coupling partners (nitriles, aldehydes and 1,3-diketones) via iodine and TBHP promoted oxidative ring contraction. The present strategy involves sequential C–N bond formation, cyclization, subsequent ring contraction and dehydrogenation to afford various medicinally important benzimidazole derivatives in moderate to good yields. This operationally simple synthetic approach proceeds at room temperature under base-free condition, broadly applicable to a wide array of nitriles and aldehydes bearing oxidation prone functional groups and noteworthy to mention that various acyclic 1,3-diketones undergo selective C–C bond cleavage leading to 2-alkyl benzimidazoles under mild condition.
- Saha, Moumita,Das, Asish R.
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supporting information
p. 2520 - 2525
(2018/05/31)
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- Selective Synthesis of 2-Substituted and 1,2-Disubstituted Benzimidazoles Directly from Aromatic Diamines and Alcohols Catalyzed by Molecularly Defined Nonphosphine Manganese(I) Complex
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Herein, we present a selective synthesis of 2-substituted and 1,2-disubstituted benzimidazoles by acceptorless dehydrogenative coupling of aromatic diamine with primary alcohols. The reaction is catalyzed by a phosphine-free tridentate NNS ligand-derived manganese(I) complex.
- Das, Kalicharan,Mondal, Avijit,Srimani, Dipankar
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p. 9553 - 9560
(2018/07/21)
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- A Magnetic Heterogeneous Biocatalyst Composed of Immobilized Laccase and 2,2,6,6-Tetramethylpiperidine-1-oxyl (TEMPO) for Green One-Pot Cascade Synthesis of 2-Substituted Benzimidazole and Benzoxazole Derivatives under Mild Reaction Conditions
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The design of reusable high-performance heterogeneous catalysts via the immobilization of chemical and biochemical species on magnetic nanoparticles increases the efficiency of catalytic systems by facilitating easy, fast, and clean separation processes. Laccase and 4-amino-2,2,6,6-tetramethylpiperidine-1-oxyl were separately immobilized on amine functionalized iron (II, III) oxide nanoparticles with covalent bonding using glutaraldehyde as a coupling reagent. The prepared catalyst was used to synthesize 12 benzoxazole and benzimidazole derivatives. The one-pot, two-step enzymatic aerobic oxidation reaction included the condensation of in situ-produced salicylaldehyde derivatives with aromatic amines, followed by an enzymatic dehydrogenation process. Optimal reaction conditions consisted of a citrate buffer (10 mM, pH 4.5) at 40 °C for an incubation time of 10 h and a heterogeneous catalyst containing immobilized laccase (80 mg, 100 U) and immobilized 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO) (40 mg, 2 mol%). The catalyst retained more than 85% of its initial activity after 10 runs. In addition to the potential for reuse without significant losses in performance, eco-friendly attributes of this catalytic system include its high catalytic activity and the ease with which it can be recovered from the reaction mixture using an external magnet. (Figure presented.).
- Mogharabi-Manzari, Mehdi,Kiani, Mahshid,Aryanejad, Sima,Imanparast, Somaye,Amini, Mohsen,Faramarzi, Mohammad Ali
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p. 3563 - 3571
(2018/09/22)
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- A practical green synthesis and biological evaluation of benzimidazoles against two neglected tropical diseases: Chagas and leishmaniasis
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Antimicrobial resistance is an ever-increasing problem throughout the world and has already reached severe proportions. Two very common neglected tropical diseases are Chagas' disease and leishmaniasis. Chagas' disease is a severe health problem, mainly in Latin America, causing approximately 50000 deaths a year and millions of people are infected. About 25-30% of the patients infected with Trypanosoma cruzi develop the chronic form of the disease. On the other hand, Leishmaniasis represents complex diseases with an important clinical and epidemiological diversity. It is endemic in 88 countries 72 of which are developing countries and it has been estimated that are 12 million people infected and 350 million are in areas with infection risk. On this basis, research on organic compounds that can be used against these two diseases is an important target. A very simple, green, and efficient protocol is developed in which bismuth nitrate pentahydrate is employed as a Lewis acid catalyst in aqueous media under microwave irradiation for the synthesis of various 2-aryl substituted benzimidazoles from aldehydes and o-phenylenediamine. Other salient features of this protocol include milder conditions, atom-economy, easy extraction, and no wastes. Nine 1H-benzimidazole derivatives (1-9) with substituents at positions 2 and 5 were synthesized and the structure of the compounds was elucidated by spectroscopic methods. The compounds were screened to identify whether they posses pharmacological activity against Chagas' disease and leishmaniasis. Compound 8 showed better activity than the control Nifurtimox against INC-5 Trypanosoma cruzi strain whereas compounds 3 and 9 have demonstrated potent leshmanicidal activity. A systematic green synthetic procedure and in vitro biological evaluation of nine 1H-benzimidazoles are described.
- Bandyopadhyay, Debashis,Samano, Selina,Villalobos-Rocha, Juan Carlos,Sanchez-Torres, Luvia Enid,Nogueda-Torres, Benjamin,Rivera, Gildardo,Banik, Bimal K.
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p. 4714 - 4725
(2018/02/14)
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- Highly reusable support-free copper(II) complex of para-hydroxy-substituted salen: Novel, efficient and versatile catalyst for C─N bond forming reactions
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An air-stable, highly active and versatile method for C─N bond forming reactions is reported. Under mild conditions using a highly reusable support-free Cu(II)–salen complex, structurally diverse N-aryl-substituted compounds were obtained via direct C─N bond forming reaction of HN-heterocycles with aryl iodides or three-component C─N bond forming reaction of 2-bromobenzaldehyde, aniline derivatives and sodium azide in good to excellent yields. C─N bond forming reaction for benzimidazole derivatives was also performed in the presence of the catalyst under ambient conditions. A series of hybrid benzimidazoles bearing morpholine, tetrazole and quinoxaline backbones were produced using this method. All reactions were performed in short times under air. The Cu(II) catalyst could be reused up to eight times in the direct cross-coupling reaction of 9H–carbazole with iodobenzene without any decrease in its catalytic activity.
- Sharghi, Hashem,Aberi, Mahdi,Shiri, Pezhman
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- Five-membered N-Heterocycles Synthesis Catalyzed by Nano-silica Supported Copper(II)–2-imino-1,2-diphenylethan-1-ol Complex
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Abstract: In this study, a new amino functionalized nano silica was synthesized using 2-hydroxy-1,2-diphenylethan-1-one. The new 2-hydroxy-1,2-diphenylethan-1-one@amino functionalized nano-silica was used as a support material for copper(II) catalyst. This composite was characterized by various techniques such as transmission electron microscopy, field emission scanning electron microscope, X-ray powder diffraction, inductively coupled plasma, energy dispersive X-ray spectroscopy, thermal gravimetric and FT-IR analysis and its particles size was estimated to be between 20 and 30?nm. The catalyst was tested in the N-heterocycles synthesis via C–N bond forming reactions. The catalyst displayed outstanding catalytic activity for all reactions under mild conditions. Finally, the nano heterogeneous copper catalyst is recoverable up to 12 times without any significant leaching which indicated that the heterogeneous catalyst is stable and very active under the applied conditions. Graphical Abstract: [Figure not available: see fulltext.]
- Sharghi, Hashem,Shiri, Pezhman,Aberi, Mahdi
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p. 2844 - 2862
(2017/09/25)
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- In water–ultrasound-promoted synthesis of tetraketones and 2-substituted-1H-benzimidazoles catalyzed by BiOCl nanoparticles
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A highly efficient, green protocol has been developed for the synthesis of various structurally diverse 2,2′-arylmethylene bis(3-hydroxy-5,5-dimethyl-2-cyclohexene-1-one) and 2-substituted-1H-benzimidazole derivatives. The reaction was performed in water under ultrasound irradiation, using BiOCl nanoparticles as a catalyst. The nanocatalyst was found to be reusable for seven subsequent reactions without much loss in activity. Simple methodology with short reaction times and mild reaction conditions with easy work-up procedure are the salient features of this method.
- Sapkal, Bharatkumar M.,Labhane, Prakash K.,Satam, Jitendra R.
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p. 4967 - 4979
(2017/07/22)
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- Facile and efficient aerobic one-pot synthesis of benzimidazoles using Ce(NO3)3·6H2O as promoter
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A series of 2-substituted benzimidazoles was synthesized under aerobic conditions, by simply heating 1,2-diaminobenzene and aldehydes in DMF at 80 °C, employing Ce(NO3)3·6H2O as promoter and atmospheric air as an efficient oxidant. The procedure afforded the products from good to excellent yields. Furthermore, this new economic and eco-friendly protocol avoids the use of toxic metal catalysts, as well as additional bases and oxidants.
- Martins, Guilherme M.,Puccinelli, Thiago,Gariani, Rogério A.,Xavier, Fernando R.,Silveira, Claudio C.,Mendes, Samuel R.
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supporting information
p. 1969 - 1972
(2017/04/27)
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