Encapsulation of a copper(II) tetradentate Schiff base complex in zeolite NaY: an efficient heterogeneous catalyst for the synthesis of benzimidazoles

Benzimidazole is a heterocyclic moiety of immense importance as it acts as a primary “biolinker” in diverse synthetic routes to obtain bioactive compounds. Substituted benzimidazoles are known to possess a varied range of pharmacological applications, namely, anti‐cancer, anti‐diabetic, anti‐inflammatory, and antiviral like anti‐HIV and anti‐fungal. A number of reviews covering the important aspects of benzimidazoles such as pharmacological activities, SAR studies, and well‐known methods of synthesis have appeared in the literature. However, green synthetic methods particularly using transition metal (TM) catalysts and their nanoparticles, although being more viable and extensively applied by researchers in the present scenario, have not been exclusively and expansively reviewed. Besides this, the vital precursors required for knitting the skeleton of benzimidazole are mainly o‐aryldiamines. The conventional synthesis generally involved the condensation of these diamines with carbonyl/carboxylic acid derivatives either via high temperature heating or via adding strong acids, mostly resulting in poor yields or mixtures. However, recent trends are replacing these conditions by mild and green conditions through TM catalysts. Therefore, the current review emphasizes on the recent trends adopted in the synthesis of benzimidazoles using condensation reaction of o‐phenylenediamines and various aldehydes/ester/amide/alcohols with TM in a catalytic role in nanoform and under environmentally benign green conditions.

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“…for synthesizing benzimidazoles ( 133 ) in 60–80% yield. The reactants were refluxed in acetonitrile for 60–80 min (Scheme ) .…”

Section: Other Important Coupling Reactionsmentioning

confidence: 99%

Recent Trends in the Synthesis of Benzimidazoles From o‐Phenylenediamine via Nanoparticles and Green Strategies Using Transition Metal Catalysts

Singhal

Khanna

Panda

et al. 2019

Journal of Heterocyclic Chem

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“…Because of their highly efficient catalytic activity, Schiff bases have been extensively studied, [9][10][11][12][13][14][15] with catalytic degradation of Schiff base complexes gaining popularity in recent years. Because of their highly efficient catalytic activity, Schiff bases have been extensively studied, [9][10][11][12][13][14][15] with catalytic degradation of Schiff base complexes gaining popularity in recent years.…”

Section: Introductionmentioning

confidence: 99%

“…Schiff bases (also called imine) are organic compounds with a carbon-nitrogen double bond (-N=C-). Because of their highly efficient catalytic activity, Schiff bases have been extensively studied, [9][10][11][12][13][14][15] with catalytic degradation of Schiff base complexes gaining popularity in recent years. [16] In general, the catalytic center of metal ions plays a very significant role in electron transfer.…”

Section: Introductionmentioning

confidence: 99%

Phosphorus‐based Schiff bases and their complexes as nontoxic antioxidants: Structure–activity relationship and mechanism of action

Zoubi

Kim

Al‐Hamdani

et al. 2019

Applied Organom Chemis

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Phosphorus-based Schiff base were synthesized by treating bis{3-[2-(4-amino-1.5-dimethyl-2-phenyl-pyrazol-3-ylideneamino)ethyl]-indol-1-ylmethyl}phosphinic acid with paraformaldehyde and characterized as a novel antioxidant. Its corresponding complexes [(VO) 2 L(SO 4 ) 2 ], [Ni 2 LCl 4 ], [Co 2 LCl 4 ], [Cu 2 LCl 4 ], [Zn 2 LCl 4 ], [Cd 2 LCl 4 ], [Hg 2 LCl 4 ], [Pd 2 LCl 4 ], and [PtLCl]Cl 2 were analyzed by Fourier transform-infrared, ( 1 H and 13 C) nuclear magnetic resonance, and mass and UV-Vis spectroscopy. Experimental data showed that the ligand coordinated with the metal ions via donor atoms such as nitrogen to form an octahedral arrangement of the Schiff base around the central transition-metal atom. The nature of these complexes was identified using the molar ratio and Job's methods, with the results agreeing with a metal-toligand (M:L) molar ratio of 2:1, expect for Pt, whose M:L was 1:1. Thermodynamic activation parameters such as ΔE*, ΔH*, ΔS*, ΔG*, and K were determined from the thermogravimetric analysis curve using the Coats-Redfern method. The antioxidant activities of the prepared compounds were assessed by using 1.1-diphenyl-2-picrylhydrazyl as the free radical, and the results show that the complex Schiff bases were found to possess potent antioxidant activity. The structure-activity relationship of the ligand and its complexes indicates that the presence of electron-donating moieties, such as Co(II) and Ni(II), in the chemical structure increases the antioxidant activity, whereas the Pt(IV) and Pd(II) complexes diminished the antioxidant activity, indicating the superior activity of the hydroxyl radical (OH · ) over the superoxide radical.

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“…In the last decade, the fabrication and design of organicinorganic hybrid porous materials, such as zeolite, microporous and mesoporous supported Schiff base complexes as heterogeneous catalysts have given widely attention in industries and catalyst filed [1][2][3]. The silica mesoporous material has two important properties: high surface area ([1000 m 2 g -1 ), high pore volume (1.3 cm 3 g -1 ), large pore size in the range 20-100 Å and great diversity in surface functionalization Compared to that of zeolites which allows them to be host for entry of bulkier guest molecules such as organometallic compounds and enzymes [4][5][6].…”

Section: Introductionmentioning

confidence: 99%

Synthesis and characterization of Ni and Zn Schiff base complexes supported on modified MCM-41 as reusable catalysts for various oxidation reactions

Noori

Nikoorazm

Ghorbani‐Choghamarani

2015

J Porous Mater

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Using post grafting method, two hybrids composite materials were prepared by anchoring Nickel and Zinc Schiff base complexes onto amino-modified MCM-41(Ni-MCM-41 and Zn-MCM-41). The prepared catalysts have been characterized by FT-IR spectroscopy, thermogravimetric analysis, and transmission electron microscopy, powder X-ray diffraction and N 2 adsorptiondesorption isotherms. The catalysts showed excellent catalytic efficiency in oxidation reaction of sulfides to sulfoxides and oxidative coupling of thiols to their corresponding disulfides using urea hydrogen peroxide as oxidant under mild reaction conditions. The supported Schiff base complexes can be recovered easily and reused many times without significant loss in catalytic activity and selectivity.

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Encapsulation of a copper(II) tetradentate Schiff base complex in zeolite NaY: an efficient heterogeneous catalyst for the synthesis of benzimidazoles

Cited by 16 publications

References 31 publications

Recent Trends in the Synthesis of Benzimidazoles From o‐Phenylenediamine via Nanoparticles and Green Strategies Using Transition Metal Catalysts

Recent Trends in the Synthesis of Benzimidazoles From o‐Phenylenediamine via Nanoparticles and Green Strategies Using Transition Metal Catalysts

Phosphorus‐based Schiff bases and their complexes as nontoxic antioxidants: Structure–activity relationship and mechanism of action

Synthesis and characterization of Ni and Zn Schiff base complexes supported on modified MCM-41 as reusable catalysts for various oxidation reactions

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