Nanocrystalline magnesium oxide: a novel and efficient catalyst for facile synthesis of 2,4,5-trisubstituted imidazole derivatives

Abstract  

Nanocrystalline magnesium oxide with high specific surface area has been used as a novel and efficient catalyst for an improved and rapid synthesis of biologically active 2,4,5-trisubstituted imidazoles, by three-component, one-pot condensation of 1,2-diketones and aryl aldehydes, in excellent yields under solvent-free and conventional heating conditions. The method has several advantages, for example excellent yields, shorter reaction time, and use of a non-toxic and recyclable catalyst.     

Simple and Efficient Method for the Synthesis of Highly Substituted Imidazoles Catalyzed by Benzotriazole

Benzotriazole is an efficient, readily available, and simple catalyst for the synthesis of 2,4,5‐trisubstituted imidazoles in high yields from 1,2‐diketones and aldehydes in the presence of NH₄OAc via multi‐components reaction. The significant features of this one‐pot procedure are very simple operation, easy work‐up and purification of products.     

Ytterbium triflate as an efficient catalyst for one-pot synthesis of substituted imidazoles through three-component condensation of benzil, aldehydes and ammonium acetate

Yb(OTf)₃ has been found to be an extremely efficient catalyst for the preparation of imidazoles derivatives via three-component coupling reactions of benzil, aldehydes and ammonium acetate under mild conditions. The process presented here is operationally simple, environmentally benign and has excellent yield. Furthermore, the catalyst can be recovered conveniently and reused for at least three reaction cycles without any loss of activity.     

Zwitterionic‐Type Molten Salt‐Catalyzed Multicomponent Reactions: One‐Pot Synthesis of Substituted Imidazoles Under Solvent‐Free Conditions

4‐(1‐Imidazolium) butane sulfonate is an excellent catalyst for the synthesis of 2,4,5‐trisubstituted and 1,2,4,5‐tetrasubstituted imidazoles through the condensation of 1,2‐dicarbonyl compounds, aldehydes, and ammonium acetate or amine via multicomponent condensation strategy under solvent‐free conditions. The key advantages of this process are high yields, reusability of catalyst, environmental friendliness, easy work‐up and purification of products by nonchromatographic methods.     

Synthesis of 2,4,5-triaryl and 1,2,4,5-tetraaryl imidazoles using silica chloride as an efficient and recyclable catalyst under solvent-free conditions

An efficient solvent-free synthesis of various 2,4,5-triaryl imidazoles and 1,2,4,5-tetraaryl imidazoles has been developed using silica chloride as a heterogeneous catalyst. The present methodology offers several advantages, such as excellent yields, shorter reaction times, economic availability, and reusability of catalyst.     

KIT‐6 Mesoporous Silica‐coated Magnetite Nanoparticles: A Highly Efficient and Easily Reusable Catalyst for the Synthesis of Benzo[d]imidazole Derivatives

KIT‐6 mesoporous silica‐coated magnetite nanoparticles as highly ordered large‐pore nanoparticles supply an environmentally friendly procedure for the synthesis of benzo[d]imidazoles through condensation of 1,2‐diaminobenzene with aryl aldehydes. These compounds were obtained in high yields and short reaction times. The catalyst could be easily recovered using an external magnet and reused for six cycles with almost consistent activity. All of the synthesized compounds were characterized by their physical constant, comparison with authentic samples, ir, 1H nmr, 13C nmr spectroscopy, and elemental analysis.     

Novel and efficient multifunctional periodic mesoporous organosilica supported benzotriazolium ionic liquids for reusable synthesis of 2,4,5-trisubstituted imidazoles

A series of periodic mesoporous organosilica supported benzotriazolium ionic liquids were synthesized and tested as effective and practical heterogeneous catalysts in the condensation reaction of diphenylethanedione, aromatic aldehydes and ammonium acetate. The catalyst PMO@ILBF4(1.0) showed brilliant catalytic activity for the synthesis of 2,4,5-trisubstituted imidazoles with good to high yields. We also found that the catalytic activity could be significantly influenced by the loading levels and functional anions of the benzotriazolium-cation ionic liquid, probably due to an intensification of intramolecular synergistic effect. Furthermore, the multifunctional catalyst PMO@ILBF4(1.0) could be easily recovered by filtration and recycled for six times with no significant loss in activity, indicating its excellent stability and reusability. This method provides an efficient and environmentally-friendly procedure for the production of 2,4,5-trisubstituted imidazoles.     

A novel bioglycerol-based recyclable carbon catalyst for an efficient one-pot synthesis of highly substituted imidazoles

The new bioglycerol-based carbon catalyst acts as an efficient, readily available, and reusable catalyst for the synthesis of 2,4,5-trisubstituted imidazoles/1,2,4,5-tetrasubstituted imidazoles, when aromatic aldehyde, ammonium acetate/amine, and 1,2-diketone are reacted in acetonitrile.     

Multi-component synthesis of highly substituted imidazoles catalyzed by nanorod vanadatesulfuric acid

Nanorod vanadatesulfuric acid (VSA NRs), as a recyclable and eco-benign catalyst, was used for one-pot synthesis of 2,4,5-trisubstituted imidazoles and 1,2,4,5-tetrasubstituted imidazoles using aldehydes, benzil, benzoin or 9,10-phenanthrenequinone and ammonium acetate or aniline under solvent-free conditions providing high to excellent yields. VSA is easily prepared by a simple reaction of chlorosulfonic acid and sodium metavanadate in high purity. As compared with the conventional procedures, the present protocol offers several advantages such as simplicity of procedure, short reaction time, high yields, easy workup, recoverability and reusability of the catalyst and simple purification of the products.     

Carbon-Based Solid Acid as An Efficient and Reusable Catalyst for One-Pot Synthesis of Tetrasubstituted Imidazoles under Solvent-Free Conditions

Carbon‐based solid acid catalyst was found to be highly efficient, eco‐friendly and recyclable heterogeneous catalyst for the multicomponent reaction of benzil, aromatic aldehyde, primary amine and ammonium acetate, giving rise to 1,2,4,5‐tetrasubstituted imidazoles in good to excellent yields. The present methodology offers several advantages, such as high yields, short reaction time, mild reaction condition and a recyclable catalyst with a very easy work up.     

Mechanism of imidazole catalysis in the curing of epoxy resins

The mechanism of imidazole catalysis in the curing of epoxy resins was studied using the PGE/1-methylimidazole, 2-methylimidazole, and 1,2-dimethylimidazole model systems and another model system based on trichloromethylethylene oxide. It was demonstrated that imidazolium systems, generated in the curing reaction, show an inherent instability leading to cleavage of an N? C bond or the 2-C? H bond (2-unsubstituted imidazoles). Fourier-transform infrared spectroscopy was used to follow specific changes in the IR spectrum of the curing mixture during polymerization. The identification of carbonyl absorptions occurring during the polymerization led to the conclusion that ketone formation is a general occurrence in the cure of epoxides with nitrogen compounds. We have also shown that imidazoles are regenerated during the curing process by at least two routes. One pathway for the regeneration of the catalyst involves N-dealkylation of the imidazole via a substitution process. Another route, β-elimination, afforded carbonyl compounds, which account for the previously unexplained appearence of infrared bands in the 1650–1770 cm^?1 region during the curing process. These investigations demonstrated the true catalytic function of the imidazole. Possible mechanisms for the regeneration of the catalyst are also suggested.     

Physicochemical studies of molecular hyperpolarizability of imidazole derivatives

A series of substituted imidazoles have been synthesized in very good yield under solvent free condition by grinding 1,2-diketone, arylaldehyde, arylamine and ammonium acetate in the presence of molecular iodine as the catalyst. The short reaction time, good yield and easy workup make this protocol practically and economically attractive and the imidazoles are characterized by NMR spectra, X-ray, mass and CHN analysis. The push-pull character of series of imidazoles have been analyzed by the quotient of the occupations of the bonding (π) and anti-bonding (π*) orbitals of the central linking -N=C-C=C- unit. Excellent correlation of the push-pull parameter with the corresponding bond lengths d(CN) and d(CC) strongly recommend both the occupation quotients (π*/π) and the corresponding bond lengths are reasonable sensors for quantifying the push-pull character and for the molecular hyperpolarizability ?(0) of these compounds. To support the experimental results, theoretical calculations (heat of formation, NLO, NBO and vibrational analysis) were also made. Within this context, reasonable conclusions concerning the steric hindrance in the chromospheres, push-pull character, hyperpolarizability of the imidazoles and their application as NLO materials will be drawn.     

An expedient one-pot synthesis of highly substituted imidazoles using supported ionic liquid-like phase（SILLP） as a green and effcient catalyst and evaluation of their anti-microbial activity

An effcient method for the synthesis of imidazole derivatives by a three-component condensation of benzil or 9,10-phenanthrenequinone,aldehydes and ammonium acetate using supported ionic liquidlike phase（SILLP）catalyst under ultrasonic irradiation or classical heating conditions is reported.The present methodology offers several advantages,such as excellent yields,simple procedures,short reaction times,simple work-up and mild conditions.The catalyst is easily separated from the products by fltration and also exhibits remarkable reusable activity.These highly substituted imidazoles were also evaluated for their anti-microbial activity.     

Benzotriazole: an excellent ligand for Cu-catalyzed N-arylation of imidazoles with aryl and heteroaryl halides

Benzotriazole (BtH) is an efficient ligand for the Cu-catalyzed N-arylation of imidazoles with aryl and heteroaryl halides. A combination of CuI/BtH was found to be an efficient and inexpensive catalyst system to carry out the N-arylation of imidazoles affording the corresponding products in good to excellent yields.     

One-pot synthesis of multisubstituted imidazoles catalyzed by Dendrimer-PWA<Superscript>n</Superscript> nanoparticles under solvent-free conditions and ultrasonic irradiation

An efficient, green and eco-friendly protocol has been developed for the synthesis of 2,4,5-trisubstituted and 1,2,4,5-tetrasubstituted imidazoles via one-pot condensation reaction using Dendrimer-PWAⁿ as catalyst under solvent-free conditions or ultrasonic irradiation in excellent yields. The reactions under conventional heating conditions were compared with the ultrasonic-assisted reactions. The operational simplicity, practicability and applicability of this protocol to various substrates make it an interesting alternative to previous procedures. The present methodology offers several advantages such as excellent yields, short reaction times, a cleaner reaction, and the absence of any tedious work-up or purification. The catalyst is easily separated from the products by filtration and also exhibits remarkable reusable activity. SEM, BET and DLS of the catalyst were also investigated after each reaction cycle.     

l-Proline: an efficient catalyst for the one-pot synthesis of 2,4,5-trisubstituted and 1,2,4,5-tetrasubstituted imidazoles

A simple highly versatile and efficient synthesis of 2,4,5-trisubstituted imidazoles is achieved by three-component cyclocondensation of 1,2-dicarbonyl compound, aldehyde and ammonium acetate using l-proline as a catalyst in methanol at moderate temperature. To explore the utility of this method 1,2,4,5-tetrasubstituted imidazoles were also synthesized. The key advantages of this process are high yields, cost effectiveness of catalyst, easy work-up and purification of products by non-chromatographic methods.     

Stripping off water at ambient temperature: direct atom-efficient acetal formation between aldehydes and diols catalyzed by water-tolerant and recoverable vanadyl triflate

[reaction: see text]. Aromatic aldehydes can be readily protected as acetals with 1,2- and 1,3-diols by using vanadyl triflate as a catalyst in CH(3)CN at ambient temperature. Carbohydrate-based 1,2- and 1,3-diols can similarly be protected in good to excellent yields. The catalyst can be readily recovered from the aqueous layer. In combination with vanadyl triflate-catalyzed sequential regioselective, reductive acetal opening and chemoselective acylations, the title method allows for differential functionalization of all four hydroxyl units in a given glucopyranoside.     

Synthesis of quinoxaline derivatives catalyzed by PEG-400

<正>Polyethylene glycol(PEG) was found to be an effective catalyst for the condensation of 1,2-diamines with 1,2-dicarbonyl compounds to afford the corresponding quinoxaline derivatives in excellent yields under mild reaction conditions.     

聚(4-乙烯基吡啶)硫酸氢盐: 一个新的高效催化剂用于无溶剂条件下合成13-芳香基-茚并 [1,2-b] 石脑油 [1,2-e] 吡喃-12(13H)-酮（英文）简

An facile and efficient protocol for the synthesis of 13-aryl-indeno[1,2-b]naphtha[1,2-e]pyran- 12(13H)- ones has been developed that proceeds via the one-pot three-component sequential reaction of an aromatic aldehyde with β-naphthol and 2H-indene-1,3-dione under solvent-free conditions in the presence of a poly(4-vinylpyridinium)hydrogen sulfate (P(4-VPH)HSO₄) catalyst. The catalyst can be reused several times, making this procedure facile, practical, and sustainable. The simple experimental procedure, solvent-free reaction conditions, use of an inexpensive catalyst, short react time, and excellent yields are some of the major advantages of this methodology.     

Simple,Efficient, and Convenient One‐Pot Synthesis of Imidazole Derivatives in the Presence of Nanosilica‐supported Imidazolium Ionic Liquid as a Catalyst

An efficient and simple synthesis of 2,4,5‐trisubstituted imidazoles is achieved by three‐component cyclocondensation of benzil, aldehyde, and ammonium acetate by using nanosilica‐supported imidazolium ionic liquid as a catalyst under solvent‐free conditions. The key advantages of this process are high to excellent yields, short reaction time, easy work‐up, and the reusability of the catalyst.