N-Sulfonic acid poly(4-vinylpyridinium) hydrogen sulfate as an efficient and reusable solid acid catalyst for one-pot synthesis of xanthene derivatives in dry media under ultrasound irradiation

N-Sulfonic acid poly(4-vinylpyridinium) hydrogen sulfate catalyzed efficiently the synthesis of xanthene derivatives under ultrasonic irradiation at room temperature, which has prompted various concerns involving cost and environmental persistence. This methodology shows the effect of presence of anion hydrogen sulfate as an important and effective factor on the promotion of the one-pot multi-components and condensation reactions. The catalyst can be recovered by simple filtration and used for several times without a significant loss of catalytic activity.     

Introduction of poly(4-vinylpyridinium) perchlorate as a new,efficient, and versatile solid acid catalyst for one-pot synthesis of substituted coumarins under ultrasonic irradiation

Poly(4-vinylpyridinium) perchlorate, is a supported, recyclable, eco-benign catalyst for synthesis of substituted coumarins via Pechmann reaction using ultrasound irradiation at room temperature and neat condition in high yields with short reaction times. The catalyst was studied by FT-IR, X-ray diffraction, scanning electron microscope, thermo-gravimetric and energy dispersion X-ray analyses. All the products were extensively characterized by ¹H NMR, FT-IR, MS and melting point analyses. This methodology offers momentous improvements over various options for the synthesis of coumarins with regard to yield of products, simplicity in operation and green aspects by avoiding toxic catalysts and solvents. Further, the catalyst can be reused and recovered for several times without loss of activity.     

Ultrasound assisted the chemoselective 1,1-diacetate protection and deprotection of aldehydes catalyzed by poly(4-vinylpyridinium)hydrogen sulfate salt as a eco-benign,efficient and reusable solid acid catalyst

Poly(4-vinylpyridinium) hydrogen sulfate solid acid was found to be efficient catalyst for preparation of 1,1-diacetate using ultrasound irradiation at ambient temperature and neat condition. Deprotection of the resulting 1,1-diacetates were achieved using the same catalyst in methanol solvent under ultrasound irradiation at room temperature. This new method consistently has the advantage of excellent yields and short reaction times. Utilization of solvent free, simple reaction conditions, isolation, and purification makes this manipulation very interesting from an economic and environmental perspective. Further, the catalyst can be reused and recovered for several times.     

Ultrasound-assisted biodiesel production by a novel composite of Fe(III)-based MOF and phosphotangestic acid as efficient and reusable catalyst

In this work, esterification of oleic acid by various alcohols is achieved with high yields under ultrasonic irradiation. This reaction performed with a novel heterogeneous catalyst that fabricated by heteropoly acid and Fe(III)-based MOF, namely MIL-53 (Fe). Syntheses of MIL-53 and encapsulation process carry out by ultrasound irradiation at ambient temperature and atmospheric pressure. The prepared composite was characterized by various techniques such as XRD, FT-IR, SEM, BET and ICP that demonstrate excellent catalytic activities, while being highly convenient to synthesize. The obtained results revealed that ultrasound irradiation could be used for the appropriate and rapid biodiesel production.     

Poly(4-vinylpyridinium)hydrogen sulfate: a novel and efficient catalyst for the synthesis of 14-aryl-14H-dibenzo[a,j]xanthenes under conventional heating and ultrasound irradiation

A simple and convenient procedure for the synthesis of 14-aryl-14H-dibenzo[a,j]xanthenes is described through a one-pot condensation of 2-naphthol with aryl aldehydes in the presence of poly(4-vinylpyridinium)hydrogen sulfate as an efficient, cheap, readily synthesized and eco-friendly catalyst in a solvent free media using conventional heating and ultrasound irradiation.     

Fractional distribution of graphene oxide and its potential as an efficient and reusable solid catalyst for esterification reactions

Graphene oxide (GrO) prepared by the Hummers method was separated into three different fractions (GrO₅₀₀₀, GrO₂₀₀₀, and GrO_res) on the basis of their dispersion stability in the water. Infrared, nuclear magnetic resonance, X‐ray photoelectron spectroscopy, and elemental analyses revealed that GrO₅₀₀₀ possesses a high degree of oxygen functionalities including phenolic, carboxylic, and ?OSO₂H groups, compared with the other fractions. The GrO₅₀₀₀ was found to be a highly efficient and reusable solid catalyst for the esterification of various carboxylic acids with a variety of alcohols to furnish corresponding esters in high to excellent yields. The catalytic activity of the GrO₅₀₀₀ was attributed to the ability of highly polar GrO₅₀₀₀ scaffold to adsorb/attract reactants, where the acid functionalities of GrO₅₀₀₀ facilitated the esterification process efficiently. The chemical and structural features of GrO₅₀₀₀ were discussed to understand the improved catalytic activity compared with GrO₂₀₀₀ and conventional solid acid catalysts. Copyright © 2014 John Wiley & Sons, Ltd.     

Ultrasound-assisted green synthesis of Ru supported on LDH-CNT composites as an efficient catalyst for N-ethylcarbazole hydrogenation

N-ethylcarbazole/dodecahydro-N-ethylcarbazole (NEC/12H-NEC) is one of the most attractive LOHCs, and it is of great significance to develop catalysts with high activity and reduce the hydrogen storage temperature. Layered double hydroxides-carbon nanotubes composites (LDH-CNT) were synthesized by a simple in-situ assembly method. Due to the introduction of CNT, a strong interaction occurred between LDH and CNT, which effectively improved the electron transfer ability of LDH-CNT. Ru/LDH-CNT catalysts were prepared via ultrasound-assisted reduction method without adding reducing agents and stabilizers. Under the cavitation effect of ultrasound, the hydroxyl groups on the surface of LDH were excited to generate hydrogen radicals (•H) with high reducibility, which successfully reduced Ru³⁺ to Ru NPs. Ru/LDH-3.9CNT-(300-1) catalyst was of 1.63 nm average Ru particle size with CNT amount of 3.9 wt% and the ultrasonic power of 300 W at 1 h, and its electron transfer resistance was less than that of Ru/LDH-(300-1). The synergy of ultrafine Ru NPs and fast electron transfer made it exhibit exceptional catalytic performance in NEC hydrogenation. Even if the reaction temperature was lowered to 80 °C, its hydrogenation performance was better than that of commercial Ru/Al₂O₃ catalyst at 120 °C. The ultrasound-assisted method is efficient, green and environmentally friendly, and the operation process is simple and economical. It is expected to be used in practical industrial production, which provides a reference for the preparation of high-activity and low-temperature hydrogen storage catalysts.     

Three-component one-pot synthesis of 4,6-diarylpyrimidin- 2(1H)-ones under solvent-free conditions in the presence of sulfamic acid as a green and reusable catalyst

A rapid and efficient one-pot method for the synthesis of 4,6-diarylpyrimidin-2(1H)-ones and related heterocycles is described. The condensation of acetophenone derivatives, aldehydes and urea in the presence of sulfamic acid was employed to synthesize a variety of pyrimidinones in moderate to excellent yields. The scope and limitations of this method are described.     

Ultrasound-assisted synthesis of 1,8-dioxo-octahydroxanthene derivatives catalyzed by p-dodecylbenzenesulfonic acid in aqueous media

An efficient and convenient approach to the synthesis of 3,3,6,6-tetramethyl-9-aryl-1,8-dioxo-octahydroxanthene derivatives using p-dodecylbenzenesulfonic acid (DBSA) as the catalyst (10 mol.%) under ultrasound irradiation is described. This method provides several advantages such as environment friendliness, high yields and simple work-up procedure. In addition, water was chosen as a green solvent.     

An efficient and practical synthesis of bis(indolyl)methanes catalyzed by aminosulfonic acid under ultrasound

Synthesis of bis(indolyl)methanes via electrophilic substitution reactions of indoles with aromatic aldehydes and ketones catalyzed by aminosulfonic acid was carried out in 23-96% yield at 30-38 degrees C in EtOH aqueous solution under ultrasound irradiation.     

Copper molybdate synthesized by sonochemistry route at room temperature as an efficient solid catalyst for esterification of oleic acid

Copper molybdate nanoplates were synthesized by a sonochemical process at room temperature, which we report as a simple and cost-effective route. Structural analysis of the material by the Rietveld method of X-ray diffraction (XRD) data revealed lindgrenite Cu₃(MoO₄)₂(OH)₂ in a single-phase structure. All the vibrational modes characteristic of the space group were identified by Raman vibrational and near-infrared (NIR) spectroscopies. The profile obtained for N₂ adsorption/desorption was type III hysteresis, characteristic of mesoporous materials, with a surface area of 70.77(1) m² g⁻¹. The micrographs of the material obtained by scanning electron microscopy showed nanoplates with nanometric sizes and an anisotropic growth aspect. The catalytic activity of lindgrenite was evaluated by esterifying oleic acid with methanol, showing high conversion rate to methyl oleate and good catalyst stability after seven recycling cycles. Above all, the best catalytic performance was reached when we optimized parameters such as oleic acid:methanol molar ratio of 1:5, 5% of catalyst dosage, and reaction time of 5 h, resulting in 98.38% of conversion at 413 K. Therefore, sonochemically synthesized lindgrenite proved to be a high potential material for biofuel production by oleic acid esterification.     

Ultrasound promoted clay catalyzed efficient and one pot synthesis of substituted oxindoles

A simple facile, one-pot synthesis of oxindoles in reasonable purity is reported via intramolecular Friedal-Craft cyclization. Clay KSF is an inexpensive, efficient and mild catalyst for the synthesis of substituted oxindoles by the reaction of chloroacetyl chloride and various anilines under the influence of ultrasonic irradiation under solvent-free conditions. The remarkable advantages of this method are the simple experimental procedures, short reaction times, high yields of products, suitability for a wide variety of substituents, and the green aspects through the avoidance of toxic catalyst and solvents.     

Application of an Mn-MOF as a highly efficient catalyst for sunlight-driven hydrogen generation

ABSTRACT

Microscale crystals of a 2D layered Mn-MOF [Mn₂(TylP)₄]_n (TylP=5-(1,2,4-triazol-1-yl)isophthalic) with a thiolate-bridged binuclear Mn(II) node similar to the active site of the [MnAu]-hydrogenase were prepared. This material shows high catalytic activity for visible-light-driven hydrogen production under the illumination of white LED or direct sunlight. The turn-over frequency of the catalyst can reach up to 6?h^?1. In this study, the heterogeneous nature and recyclability of the catalyst, as well as the factors that affect the catalytic activity have been investigated and described. Moreover, the photocatalytic mechanism for the hydrogen generation of [Mn₂(TylP)₄]_n has also been proposed, based on fluorescence spectra and cyclic voltammetry.     

A highly efficient magnetic solid acid catalyst for synthesis of 2,4,5-trisubstituted imidazoles under ultrasound irradiation

Fe₃O₄ nanoparticles were prepared by chemical coprecipitation method and subsequently coated with 3-aminopropyltriethoxysilane (APTES) via silanization reaction. Grafting of chlorosulfuric acid on the amino-functionalized Fe₃O₄ nanoparticles afforded sulfamic acid-functionalized magnetic nanoparticles (SA-MNPs). SA-MNPs was found to be a mild and effective solid acid catalyst for the efficient, one-pot, three-component synthesis of 2,4,5-trisubstituted imidazoles under ultrasound irradiation. This protocol afforded corresponding imidazoles in shorter reaction durations, and in high yields. This green procedure has many obvious advantages compared to those reported in the previous literatures, including avoiding the use of harmful catalysts, easy and quick isolation of the products, excellent yields, short routine, and simplicity of the methodology.     

CaCl2 as a bifunctional reusable catalyst: diversity-oriented synthesis of 4H-pyran library under ultrasonic irradiation

CaCl₂ is applied as an efficient reusable and eco-friendly bifunctional catalyst for the one-pot three-component synthesis of 4H-pyrans under ultrasonic irradiation. A broad range of substrates including the aromatic and heteroaromatic aldehydes, indoline-2,3-dione (isatin) derivatives, acenaphthylene-1,2-dione (acenaphthenequinone) and 2, 2-dihydroxy-2H-indene-1,3-dione (ninhydrin) were condensed with carbonyl compounds possessing a reactive ??-methylene group and alkylmalonates. All reactions are completed in short times, and the products are obtained in good to excellent yields. The catalyst could be recycled and reused several times without any loss of efficiency.     

Poly(4-vinylpyridine) supported acidic ionic liquid: A novel solid catalyst for the efficient synthesis of 2,3-dihydroquinazolin-4(1H)-ones under ultrasonic irradiation

A novel poly(4-vinylpyridine) supported acidic ionic liquid catalyst was synthesized by the reaction of 4-vinylpyridine with 1,3-propanesultone, followed by the polymerization and the addition of the heteropolyacid. Due to the combination of polymer features and ionic liquid, it acted as a heterogeneous catalyst to effectively catalyze the cyclocondensation reaction of anthranilamide with aldehydes under ultrasonic irradiation and afforded the corresponding 2,3-dihydro-4(1H)-quinazolinones compounds in good to excellent yields. In addition, the catalyst could be easily recovered by the filtration and reused six times without significant loss of catalytic activity. More importantly, the use of ultrasonic irradiation can obviously accelerate the reaction.     

Ultrasound-assisted oxidative desulfurization process of liquid fuel by phosphotungstic acid encapsulated in a interpenetrating amine-functionalized Zn(II)-based MOF as catalyst

In this work, ultrasound-assisted oxidative desulfurization (UAOD) of liquid fuels performed with a novel heterogeneous highly dispersed Keggin-type phosphotungstic acid (H₃PW₁₂O₄₀, PTA) catalyst that encapsulated into an amino-functionalized MOF (TMU-17-NH₂). The prepared composite exhibits high catalytic activity and reusability in oxidative desulfurization of model fuel. Ultrasound-assisted oxidative desulfurization (UAOD) is a new way to performed oxidation reaction of sulfur-contain compounds rapidly, economically, environment-friendly and safely, under mild conditions. Ultrasound waves can be apply as an efficient tool to decrease the reaction time and improves oxidative desulfurization system performance. PTA@TMU-17-NH₂ could be completely performed desulfurization of the model oil by 20 mg of catalyst, O/S molar ratio of 1:1 in presence of MeCN as extraction solvent. The obtained results indicated that the conversions of DBT to DBTO₂ achieve 98% after 15 min in ambient temperature. In this work, we prepared TMU-17-NH₂ and PTA/TMU-17-NH₂ composite by ultrasound irradiation for first time and employed in UAOD process. Prepared catalyst exhibit an excellent reusability without PTA leaching and loss of activity.     

Cavitational chemistry: a mild and efficient multi-component synthesis of amidoalkyl-2-naphthols using reusable silica chloride as catalyst under sonic conditions

An efficient and direct procedure for the synthesis of amidoalkyl-2-naphthol derivatives has been described. The process employs a three-component cyclocondensation reaction in one-pot using β-naphthol, aromatic aldehyde and acetamide or benzamide in the presence of silica chloride accelerated by ultrasound giving the product in excellent yield in very short duration.     

Ultrasound-promoted an efficient method for one-pot synthesis of 2-amino-4,6-diphenylnicotinonitriles in water: a rapid procedure without catalyst

A green and convenient approach to the synthesis of 2-amino-4,6-diphenylnicotinonitriles via four-component reaction of malononitrile, aromatic aldehydes, acetophenone derivatives and ammonium acetate in water under ultrasound irradiation is described. The combinatorial synthesis was achieved for this methodology with applying ultrasound irradiation while making use of water as green solvent. In comparison to conventional methods, experimental simplicity, good functional group tolerance, excellent yields, short routine, and selectivity without the need for a transition metal or base catalyst are prominent features of this sonocatalyzed procedure.