BF3·SiO2: an efficient reagent system for the one-pot synthesis of 1,2,4,5-tetrasubstituted imidazoles

Green synthesis of imidazole derivatives in a ternary deep eutectic solvent system

Deep eutectic solvents (DESs) have gained recognition for their sustainable characteristics and demonstrated potential for various applications in chemical processes. Their biodegradability and recyclability make them an attractive alternative for sustainable chemistry. Herein, we investigated the application of novel ternary DES as a reaction medium and recyclable catalyst for one-pot, multicomponent synthesis of tri and tetra-substituted imidazole derivatives under mild conditions. A ternary DES composed of dimethyl urea, SnCl2, and HCl was prepared using a simple method from readily available starting materials. The structural and chemical composition of this ternary DES was characterized using FT-IR and EDX spectroscopy. The synthesis of various substituted imidazoles using the ternary DES has resulted in good to excellent yields, with high-purity products, which were achieved in a relatively short reaction time. Ternary DES exhibited remarkable properties as a cost-effective and environmentally friendly dual solvent and catalyst. The prepared DES exhibits excellent recyclability, with no noticeable decline in its catalytic performance even after five consecutive runs.

Metal-free approach for imidazole synthesis via one-pot N-α-C(sp3)-H bond functionalization of benzylamines

A metal-free one-pot method is established for the synthesis of tetrasubstituted imidazoles from the reaction of arylmethylamines and 1,2-dicarbonyls/benzoin. The N-α-C(sp3)-H bond functionalization of arylmethylamines using a catalytic amount of AcOH afforded polysubstituted imidazoles under aerobic conditions in significant yields of up to 95%.

Various synthesis and biological evaluation of some tri -tetra-substituted imidazoles derivatives: A review

The imidazole nucleus represents a significant group of heterocyclic molecules with diverse significance in the modern world due to its exploration potential and various pharmacological applications. The relevance of imidazole and its derivatives has gained popularity in recent years, especially in the production of commercial drugs and the treatment of various conditions. The imidazole nucleus is present in many natural compounds and widely distributed in essential amino acids, such as l-histidine, whose derivatives exhibit powerful pharmacological properties. In this review, we delve into the historical timeline and development of synthetic pathways for tri- and tetra-substituted imidazoles used in the renowned Radziszewski reaction. Furthermore, we explore various bacteriological applications documented in the literature, as well as current advances in preclinical approaches to imidazole-based drug discovery. Tri- or tetra-substituted imidazole derivatives show strong potential for new synthesis methods, such as reflux or microwave, as well as various biological activities.

Magnetic polyborate nanoparticles as a green and efficient catalyst for one-pot four-component synthesis of highly substituted imidazole derivatives

In this study, magnetic polyborate nanoparticles (MPBNPs) were prepared via a simple procedure from boric acid by using ball-milling and then characterized by various spectroscopic, microscopic and analytical methods including FT-IR, EDX, XRD, FESEM, VSM and TGA analysis. The obtained MPBNPs were further explored, as a green and highly efficient catalyst, in the multi-component synthesis of a wide range of tetra-substituted imidazoles from cascade cyclocondensation as well as in situ air oxidation of benzil or benzoin, aromatic aldehydes, primary amine and ammonium acetate in EtOH, as a green solvent, under reflux conditions. Additionally, environmentally friendly conditions for the preparation of the catalyst by the use of non-toxic reactants, facile procedure and high to excellent yields of the desired products as well as the use of a green solvent are some advantages of this new protocol.

Preparation of polysubstituted imidazoles using AC-SO3H/[Urea]7[ZnCl2]2 as an efficient catalyst system: a novel method, and α-glucosidase inhibitor activity

Deep eutectic solvents (DESs) act as both an organic solvent and a useful catalyst for organic synthesis reactions, especially the synthesis of heterocyclic compounds containing the element nitrogen. DESs exhibit many important properties namely large liquid fields, biodegradability, outstanding thermal stability, and moderate vapor pressure. Amorphous carbon-bearing sulfonic acid groups (AC-SO3H) are one of the new-generation solid acids showing strong acid activity. Based on the simultaneous presence of acidic functional groups such as carboxylic acid, phenolic, and sulfonic acid groups, they exhibit many important activities namely strong Brønsted acid, high surface area, high stability, reusability, and recyclability. In this study, AC-SO3H was made from rice husk via the carbonization and sulfonation processes, and the surface properties and structure were examined using contemporary methods such as FT-IR, P-XRD, TGA, SEM, and EDS. And, [Urea]7[ZnCl2]2 was synthesized from urea and ZnCl2 with a mole ratio of 7 : 2; the structure is defined using FT-IR and TGA. By combining AC-SO3H and [Urea]7[ZnCl2]2 we aim to form an effective catalyst/solvent system for the preparation of polysubstituted imidazole derivatives through the multi-component cyclization reaction from nitrobenzenes, benzil, aldehydes, and ammonium acetate. The major products are obtained with high isolation yields above 60%. To assess the catalyst system's activity, the recovery and reusability of the AC-SO3H/[Urea]7[ZnCl2]2 system were examined with hardly any performance modification. In an effort to create potential enzyme α-glucosidase inhibitors, several novel polysubstituted imidazoles were created. Five of these compounds showed good enzyme α-glucosidase inhibitor activity. The most effective substances were IMI-13, IMI-15, and IMI-20, with IC50 values that were greater than the acarbose at 16.5, 15.8, and 11.6 μM, respectively - the acarbose (IC50, 214.5 μM) as the positive control.

Synthesis, antioxidant activity, antimicrobial efficacy and molecular docking studies of 4-chloro-2-(1-(4-methoxyphenyl)-4,5-diphenyl-1H-imidazol-2-yl)phenol and its transition metal complexes

Herein, a one-pot synthesis of tetra-substituted imidazole, 4-chloro-2-(1-(4-methoxyphenyl)-4,5-diphenyl-1H-imidazol-2-yl)phenol (HL), is reported by the reaction of benzil, 5-bromosalicylaldehyde, ammonium acetate and anisidine. The synthesized imidazole was reacted with salts of 1st row transition metals (Co(ii), Ni(ii), Cu(ii), Mn(ii) and Zn(ii)) to obtain metal complexes. The structure of the compounds was confirmed using various spectroscopic and analytical techniques. HL, which is crystalline, was characterized by SC-XRD. Subsequently, the synthesized compounds were evaluated for their antioxidant and antimicrobial activities. Antimicrobial studies revealed the more noxious nature of metal complexes compared to ligand against various strains of bacteria and fungi. Molecular docking results based on the binding energy values also supported the experimental results of the antioxidant activities of the compounds. HL was found to be a better antioxidant than metal complexes. For a better insight into the structure, computational studies of the compounds were also carried out. A clear intra-molecular charge transfer was perceived in the ligand and its metal complexes. The transfer integral values for holes (36.48 meV) were found to be higher than the electron transfer integrals (24.76 meV), which indicated that the ligand would be a better hole transporter. According to the frontier molecular orbitals of the dimer, the charge transfer within the molecule is found from monomer 1 to 2.

An efficient green protocol for the synthesis of 1,2,4,5-tetrasubstituted imidazoles in the presence of ZSM-11 zeolite as a reusable catalyst

In this study, we have synthesized a series of ZSM-11 zeolite catalysts using tetrapropyl ammonium hydroxide as a structure-directing agent through a highly efficient hydrothermal method. The series of catalysts were studied by different techniques such as FT-IR spectroscopy, XRD, FE-SEM, HR-TEM, EDS, pyridine-FT-IR spectroscopy, and BET analysis. We focused on varying reaction time intervals from 18 to 48 hours to investigate the effect on catalytic activities of the synthesized series of catalysts. The percentages of aluminum increased in the framework of zeolites with increasing crystallinity, surface area, external surface area, and acidity in the series of ZSM-11 zeolites by increasing the time from 18 to 48 h. Then, we studied the catalytic activity of a series of ZSM-11 zeolites and found that the ZSM-11 zeolite (48 h) possesses higher catalytic activity towards the synthesis of 1,2,4,5-tetrasubstituted imidazoles under solvent-free conditions. The present protocol scored well with excellent yield, short reaction time, clean reaction profiles, low catalyst loading, and no tedious workup. The catalyst (ZSM-11 zeolite 48 h) was recycled and reused in five runs without any considerable loss of activity and product yield.

Synthesis, Characterization, and Catalytic Properties of Magnetic Fe3O4@FU: A Heterogeneous Nanostructured Mesoporous Bio-Based Catalyst for the Synthesis of Imidazole Derivatives

In this protocol, Fucoidan (FU), a fucose-rich sulfated polysaccharide extracted from brown algae Fucus vesiculosus was used for in situ preparation of magnetic Fe₃O₄@FU. Nanoco magnetic properties of Fe₃O₄@FU were investigated by energy dispersive X-ray (EDX) spectroscopy, X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), Brunauer–Emmett–Teller (BET) adsorption method, and vibrating sample magnetometer (VSM). The catalytic activity of Fe₃O₄@FU was employed for the synthesis of tri- and tetra-substituted imidazoles through three- and four-component reactions respectively, between benzyl, aldehydes, NH₄OAc and benzyl, aldehydes, NH₄OAc, and amine under reflux in ethanol. It is worth nothing that excellent yields, short reaction times, chromatography-free purification, and environmental friendliness are highlighted features of this protocol.

Organocatalyzed Solvent Free and Efficient Synthesis of 2,4,5-Trisubstituted Imidazoles as Potential Acetylcholinesterase Inhibitors for Alzheimer's Disease

The catalytic potential of pyridine-2-carboxlic acid has been evaluated for efficient, green and solvent free synthesis of 2,4,5-trisubstituted imidazole derivatives 3a-3m. The compounds 3a-3m were synthesized by one pot condensation reaction of substituted aromatic aldehydes, benzil, and ammonium acetate in good to excellent yields (74-96 %). To explore the potential of these compounds against Alzheimer's disease, their inhibitory activities against acetylcholinesterase (AChE) were evaluated. In this series of compounds, compound 3m, bearing one ethoxy and a hydroxy group on the phenyl ring on 2,4,5-trisubstituted imidazoles, proved to be a potent AChE inhibitor (102.56±0.14). Structure-activity relationship (SAR) of these compounds was developed. Molecular dockings were carried out for the compounds 3m, 3e, 3k, 3c, 3a, 3d, 3j, and 3f in order to further investigate the binding mechanism. The inhibitor molecule was molecularly docked with acetylcholinesterase to further study its binding mechanism. The amino group of the compound 3m forms an H-bond with the oxygen atom of the residue (i. e., THR121) which has a bond length of 3.051 Å.

Visible light-emitting diode light-driven one-pot four component synthesis of poly-functionalized imidazoles under catalyst- and solvent-free conditions

A visible light-emitting diode light-driven green and sustainable protocol has been demonstrated for the one-pot four component synthesis of poly-functionalized imidazoles under catalyst- and solvent-free conditions.

An efficient and recyclable nanocatalyst for the green and rapid synthesis of biologically active polysubstituted pyrroles and 1,2,4,5-tetrasubstituted imidazole derivatives

An effective process for the green and rapid synthesis of biologically active polysubstituted pyrroles and 1,2,4,5-tetrasubstituted imidazoles derivatives using Cu@imine/Fe₃O₄ MNPs catalyst under solvent-free conditions is explained. This catalyst showed high reactivity for the synthesis of a set of different derivatives of polysubstituted pyrroles and 1,2,4,5-tetrasubstituted imidazole derivatives under appropriate reaction conditions and short times. Moreover, the catalyst was also recycled and reused for six runs with no considerable reduction in reactivity and yields. Compared to the reported procedures, this method consistently demonstrates the advantages of low catalyst loading, short reaction times, easy separation and purification of the products, high yields, and high recoverability and recoverability of the catalyst.

So the use of Fe₃O₄@SiO₂–ZrCl₂-MNPs leads to an improved protocol in terms of the compatibility with the environment, yields of the products, reaction times and the amount of the catalyst when compared with other catalysts.

An iodine/DMSO-catalyzed sequential one-pot approach to 2,4,5-trisubstituted-1H-imidazoles from α-methylene ketones

A sequential one-pot approach to 2,4,5-trisubstituted imidazoles has been developed from α-methylene ketones and aldehydes. This methodology employs air-moisture stable reaction conditions and an inexpensive iodine/DMSO system affording a diverse range of known and novel (substrate scope) 2,4,5-trisubstituted imidazoles in moderate to excellent yields. The iodine/DMSO system was extended to the domino convergent synthesis of two functionalized intermediates, benzil and benzaldehyde, to produce the final product.

One-pot, Multicomponent Synthesis under Microwave Conditions of New Imidazole and Acridine Benzamido Acetic Acid Derivatives

Starting from 4-aminohippuric acid (AHA), two novel series of heterocyclic compounds of pharmaceutical interest have been synthesised by one-pot, multicomponent reactions under microwave conditions. Reaction of AHA with various aldehydes and benzil in (1:1) EtOH/acetic acid in the presence of ammonium acetate yielded 1,2,3,5-tetra-arylated imidazole derivatives, whereas a solvent-free reaction of AHA with various aldehydes and dimedone (2 equiv.) in the presence of p-TSA yielded 4,9-diarylated 1,8-dioxo-decahydroacridine derivatives. These reactions produced good yields in short reaction times with an easy work-up, and purification of products was achieved by simple recrystallisation.

Multicomponent reactions: a sustainable tool to 1,2- and 1,3-azoles

The present review outlines the recent advancements and pioneering efforts on the synthesis of 1,2/1,3-azoles employing a multicomponent strategy.