Reactions In Solvent-free Conditions Research Articles

Basified Graphene Oxide and PPO Composite Aerogel with Basified Graphene Oxide for Henry Reaction in Solvent-Free Conditions: A Green Approach

Novel basified graphene oxide and high-porosity monolithic composite aerogels of poly(2,6-dimethyl-1,4-phenylene oxide) (PPO) containing basified graphene oxide (b-eGO) have been prepared as recoverable and reusable catalysts for the Henry reaction in solvent-free conditions at room temperature. The results showed that, although b-eGO was able to promote the reaction, it suffered from reduced stability. On the other hand, PPO/b-eGO aerogels were able to efficiently promote the Henry reaction in solvent-free conditions. The product could be obtained pure without a purification step, and the catalyst was stable for over 15 months and could be easily recycled without losing catalytic efficiency. The stereochemical outcome was further investigated in the presence of PPO/b-eGO. Despite its negligible influence on diastereoselectivity, better efficiency and a sensible reduction of reaction time were observed.

Immobilization of CdCl2 on filamentous silica nanoparticles as an efficient catalyst for the solvent free synthesis of some amidoalkyl derivatives

Due to desirable properties of filamentous silica nanoparticles (KCC-1), these compounds can be considered as appropriate support for the preparation of heterogeneous catalysts. In this study, immobilized CdCl2 on modified KCC-1 surfaces was fruitfully prepared. The structure of prepared catalyst was confirmed by Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), field emission scanning electron microscope (FE-SEM), transmission electron microscope (TEM), brunauer-emmett-teller (BET) and energy dispersive X-Ray (EDX) analysis. The efficiency of obtained solid acid catalyst was studied for the synthesis of some amidoalkyl naphthole and amidoalkyl naphthoquinones through a multicomponent reaction in solvent free conditions. The structure of all obtained products was characterized by analytical and spectroscopic methods.

Use of pectin as a suitable substrate for catalyst synthesis Fe3O4@Pectin@Ni (II) and its application in oxidation reaction

In this paper, the properties of a catalyst that composed of magnetic nanoparticles and Pectin biopolymer that is widely found in nature (Fe3O4@Pectin) to support nickel (II) acetate are discussed, and this catalyst was then used in response to the synthesis of aaldehyde derivatives. The heterogeneous catalyst was characterized by techniques such as FT-IR spectroscopy, FE-SEM, TEM, XRD spectroscopy, EDX spectroscopy and ICP spectroscopy. Then the catalyst was explored in the oxidation reaction of alcohols that has high efficiency and selectivity and the synthesized aldehydes. The most important advantages of this method are easy to work up procedure, perform the reaction in solvent-free conditions, and the catalyst can be separated by an external magnet and used several times without reducing the activity, which prevents environmental pollution.

Co3O4 nanoparticles embedded in triple-shelled graphitic carbon nitride (Co3O4/TSCN): a new sustainable and high-performance hierarchical catalyst for the Pd/Cu-free Sonogashira–Hagihara cross-coupling reaction in solvent-free conditions

Co3O4 nanoparticles embedded in triple-shelled graphitic carbon nitride (Co3O4/TSCN): a new sustainable and high-performance hierarchical catalyst for the Pd/Cu-free Sonogashira–Hagihara cross-coupling reaction in solvent-free conditions

1D Zn(II) Coordination Polymers as Effective Heterogeneous Catalysts in Microwave-Assisted Single-Pot Deacetalization-Knoevenagel Tandem Reactions in Solvent-Free Conditions

The new 1D CPs [Zn(L1)(H2O)4]n.nH2O (1) and [Zn(L2)(H2O)2]n (2) [L1 = 1,1′-(ethane-1,2-diyl)bis(6-oxo-1,6-dihydropyridine-3-carboxylic acid); L2 = 1,1′-(propane-1,3-diyl)bis(6-oxo-1,6-dihydropyridine-3-carboxylic acid)] were prepared from flexible dicarboxylate pro-ligands (H2L1 and H2L2). Both CPs 1 and 2 were characterized by elemental, FTIR, and powder X-ray diffraction analysis. Their geometry and the structural features were unveiled by single-crystal X-ray diffraction analysis. The underlying topology of the CPs was illustrated by the topological analysis of the H-bonded structure of CP 1, which revealed a 3,4,6-connected trinodal net. On the other hand, topological analysis on the hydrogen-bonded network of CP 2 showed a 2,3,3,4,6,7-connected hexanodal net. The thermal stability of the CPs was investigated by thermogravimetric analysis. CPs 1 and 2 act as heterogeneous catalysts in one-pot tandem deacetalization–Knoevenagel condensation reactions under environmentally mild conditions. CPs 1 exhibits a yield of ca. 91% in a microwave-assisted solvent-free medium, whereas a slightly lower yield was obtained for CP 2 (87%) under the same experimental protocol. The recyclability of catalyst 1 was also assessed. To our knowledge, these are the first Zn(II)-based CPs to be applied as heterogeneous catalysts for the above tandem reactions under environmentally friendly conditions.

CoII Immobilized on Aminated Magnetic-Based Metal–Organic Framework: An Efficient Heterogeneous Nanostructured Catalyst for the C–O Cross-Coupling Reaction in Solvent-Free Conditions

In this paper, we report the synthesis of Fe3O4@AMCA-MIL53(Al)-NH2-CoII NPs based on the metal–organic framework structures as a magnetically separable and environmentally friendly heterogeneous nanocatalyst. The prepared nanostructured catalyst efficiently promotes the C–O cross-coupling reaction in solvent-free conditions without the need for using toxic solvents and/or expensive palladium catalyst.

A simple and efficient synthesis of novel pyranothiadiazolopyrimidine derivatives by three component reactions in solvent-free conditions

A simple and efficient synthesis of novel pyranothiadiazolopyrimidine derivatives by three component reactions in solvent-free conditions

PdII Immobilized on Ferromagnetic Multi-Walled Carbon Nanotubes Functionalized by Aminated 2-Chloroethylphosphonic Acid with S-Methylisothiourea (FMMWCNTs@CPA@SMTU@PdII NPs) Applied as a Highly Efficient and Recyclable Nanostructured Catalyst for Suzuki–Miyaura and Mizoroki–Heck Cross-Coupling Reactions in Solvent-Free Conditions

The new ferromagnetic nanostructured FMMWCNTs@CPA@SMTU@PdII NPs (IV) as an eco-friendly heterogeneous nanocatalyst with a particle size of ~20–30nm reported earlier by our group has been found to be very effective for Suzuki–Miyaura and Mizoroki–Heck cross-coupling reactions at ambient temperature. The procedure has been applied for a wide range of aryl halides, arylboronic acids, and alkenes. The magnetic separation by an external magnetic field, mild reaction conditions, and catalyst reusability up to four times without significant decrease in catalytic activity (reduced catalytic activity from 11 to 18% in the fifth, sixth, and seventh cycles) made the present method sustainable and economically viable for C–C cross-coupling reactions.

The Influence of O/S Exchange on the Biocatalytical Activity of Benzisoselenazol-3(2H)-ones

The crucial feature of organoselenium compounds, when considering them as promising drug candidates in cancer therapy, is their unique ability to alter the cellular redox regulations. Organic Se-molecules continue to demonstrate a positive therapeutic effect both in cancer prevention—as antioxidants, and treatment—as prooxidants. The growing interest in this field of research highlights the need to search for particular pharmacophore motifs, which could enhance the efficiency and selectivity, and decrease the toxicity of potential anticancer agents. Herein, a series of redox-active organoselenium derivatives—N-functionalized benzisoselenazol-3(2H)-thiones, has been designed and synthetized. A new synthetic pathway, with the application of Lawesson’s reagent, has been developed and efficiently applied. The key steps involving microwave irradiation facilitated performing the reaction in solvent-free conditions, shortening the reaction time and significantly improving the overall yield of the process. Six N-alkyl derivatives have been obtained and tested as antioxidant catalysts and anti-proliferative agents. The N-propyl benzisoselenazol-3(2H)-thione was the best peroxide scavenger and the N-cyclohexyl derivative exhibited the best cytotoxic activity towards prostate cancer cell line DU145.

Highly Efficient Synthesis of 1-Thioamidoalkyl-2-naphthols and 14-Aryl-14H-dibenzo[a,j]xanthenes using a Novel Ionic Liquid: Catalyst Preparation, Characterization and Performing the Reactions

In this work, a novel Brønsted acidic ionic liquid namely triethylaminium-N-sulfonic acid trifluoroacetate {[TEASA][TFA]} has been synthesized by the reaction of NEt3 with ClSO3H, and then with CF3CO2H. The ionic liquid has been characterized by studying its spectroscopic data (1H and 13C NMR, FT-IR, and mass spectra). Afterward, it has been utilized as a highly effective and general catalyst to promote the following organic reactions in solvent-free conditions: (i) the production of 1-thioamidoalkyl-2-naphthols from arylaldehydes, 2-naphthol and thioacetamide, and (ii) the preparation of 14-aryl-14H-dibenzo[a,j]xanthenes from arylaldehydes and 2-naphthol. It is noteworthy that [TEASA][TFA] has catalyzed the reactions under milder conditions relative to most of the reported methods. Moreover, it afforded the both products in higher yields with respect to most of the previous works.

Copper Zirconium Phosphate as an Efficient Catalyst for Multi-component Reactions in Solvent-Free Conditions

Copper zirconium phosphate nanoparticles were used as a convenient and efficient catalyst for multi-component reactions in solvent-free conditions. The catalyst is easy to prepare and shows interesting catalytic properties. The catalyst was characterized by some instrumental techniques such as ICP-OES, EDS, XRD, BET, NH3-TPD, Py-FTIR, SEM, and TEM. These analyses revealed that the interlayer distance in the catalyst increased from 7.6 to 8.8 A when Cu2+ was intercalated between the layers, whereas the crystallinity of the material was reduced. The steric and electronic properties of the different substrates had a significant influence on the reaction conditions. These protocols have the advantages of inexpensive materials, mild reaction conditions, excellent yields, short reaction times, and simple and clean work-up. This work introduces a new application of this catalyst, not described in the literature up to now. In addition, the catalyst can be recovered and reused for three times without a significant loss in its activity and selectivity.

Three VO2+ complexes of the pyridoxal-derived Schiff bases: Synthesis, experimental and theoretical characterizations, and catalytic activity in a cyclocondensation reaction

Three oxovanadium(IV) complexes of the pyridoxal Schiff bases have been newly synthesized and characterized. The used Schiff bases were N,N′-dipyridoxyl(ethylenediamine), N,N′-dipyridoxyl(1,3-propanediamine) and N,N′-dipyridoxyl(1,2-benzenediamine). Also, the optimized geometry, assignment of the IR bands and the Natural Bond Orbital (NBO) analysis of the complexes have been computed using the density functional theory (DFT) methods. Dianionic form of the Schiff bases (L2−) acts as a tetradentate N2O2 ligand. The coordinating atoms of the Schiff base are the phenolate oxygens and imine nitrogens, which occupy four base positions of the square-pyramidal geometry of the complexes. The oxo ligand occupies the apical position of the [VO(L)] complexes. In the optimized geometry of the complexes, the coordinated Schiff bases have more planar structure than their free form. Due to the high-energy gaps, all of the complexes are predicted to be stable. Good agreement between the experimental values and the DFT-computed results supports suitability of the optimized geometries for the complexes. The investigated complexes show high catalytic activities in synthesis of the tetrahydrobenzo[b]pyrans through a three-component cyclocondensation reaction of dimedone, malononitrile and some aromatic aldehydes. The complexes catalyzed the reaction in solvent free conditions and the catalysts were found to be reusable.

New semi-conducting rotaxane based on β-cyclodextrin and anthracene moieties

A new rotaxane (BPAAn/β-CD), consisting of an anthracene-based semi-conducting material (BPAAn) encapsulated into β-cyclodextrin (β-CD), has been synthesized via the Williamson reaction in solvent-free conditions. The supramolecular structure of the compound was confirmed by NMR and FT-IR spectroscopies. The optical and morphological properties of this organic material were investigated by UV–visible absorption, photoluminescence spectroscopy and atomic force microscopy. BPAAn/β-CD film has an optical gap of 2.9eV and exhibits green photoluminescence. An optical gap of 2.9eV was estimated from the absorption edge of the rotaxane thin film. The BPAAn/β-CD exhibits a blue photoluminescence in dilute solution; whereas, a green emission was observed in the solid state, due to the π–π interaction in the anthracene moieties. The rotaxane shows a significantly enhanced PL quantum yield and improved film quality in comparison with the free BPAAn. The HOMO and LUMO levels were estimated using cyclic voltammetry analysis, and show enhanced electron affinity of the BPAAn in its complexed form. A single-layer device with the configuration [ITO/rotaxane/Aluminum] has been elaborated and showed low turn-on voltage of 5V.

Facile Ecofriendly Synthesis of Monastrol and Its Structural Isomers via Biginelli Reaction

In this paper, a Q-tube equipment is proposed as a valid alternative to monomode MW technology to synthesize in a simple and economic way a library of dihydropyrimidine derivatives performing the Biginelli reaction in solvent-free conditions under pressure and with the catalysis of a very mild and environmentally benign Lewis acid consisting of erbium trichloride hexahydrate.

Recyclable CuS quantum dots as heterogeneous catalyst for Biginelli reaction under solvent free conditions

CuS Quantum dots (QDs) of 2–3nm size have been synthesized in very high yield in 2min using microwave and water as medium. The obtained QDs have been characterized by UV–visible spectrophotometer, XRD, TEM and SAED. CuS QDs have been used as a nanocatalyst to carry out Biginelli reaction in solvent free conditions. CuS QDs exhibit good catalytic activity for synthesis of dihydropyrimidinones with excellent yield. The catalyst takes less time as compared to other catalysts. It has attractive features like reduced reaction time, higher yields, ease of product isolation, economic availability of catalyst, simple procedure, and no harmful byproduct. The spent heterogeneous catalyst have been recovered by simple filtration and reused for multiple cycles. Kinetic studies have been carried out for the synthesis of both CuS QDs as well as Biginelli reaction products and rate constants have also been estimated.

Microwave promoted diastereoselective synthesis of dihydroindeno[1,2-b]furans via one-pot three-component reaction in solvent-free conditions

An efficient method was developed for the synthesis of fused dihydroindeno[1,2-b]furans. One-pot three-component reaction of 1,3-indanedione, aromatic aldehyde and pyridinium ylide in the presence of triethylamine under microwave-irradiation in solvent-free conditions afforded dihydroindeno[1,2-b]furans in a diastereoselective manner in excellent yields.

Fe3O4 Nanoparticles as an Efficient and Magnetically Recoverable Catalyst for Friedel–Crafts Acylation Reaction in Solvent-Free Conditions

Application of Fe3O4 nanoparticles (NPs) as a robust, very efficient, and magnetically recoverable catalyst was investigated in Friedel–Crafts acylation (FCA) of ferrocene and aromatic compounds. This reaction was performed with acid chlorides in solvent-free conditions at room temperature. The catalyst was easily separated by an external magnetic field from the reaction mixture. The separated catalyst was recycled for several consecutive runs without appreciable loss of its catalytic activity. Supplemental materials are available for this article. Go to the publisher's online edition of Synthetic Communications® to view the free supplemental file.

Synthesis of 5-alkylated barbituric acids and 3-alkylated indoles via microwave-assisted three-component reactions in solvent-free conditions using Hantzsch 1,4-dihydropyridines as reducing agents

Reaction of barbituric acids with aldehydes and dihydropyridines in one pot under microwave (MW) irradiation in the absence of solvent, affords 55–82% of the 5-benzylated barbituric acids. Use of alkyl nitriles or barbituric acids with indole-3-aldehyde and dihydropyridine (DHP) afforded 3-alkylated indoles in 57–76 % yield. In each case DHPs are converted to pyridines.

Microwave assisted synthesis of fine chemicals in solvent-free conditions over mesoporous zirconium phosphate

Synthesis of various industrially important fine chemicals under microwave irradiation (MWI) in solvent-free conditions over mesoporous zirconium phosphate (m-ZrP) is reported. m-ZrP is synthesized by MWI in basic medium using a precursor solution of zirconium carbonate complex as zirconium source and CTAB as a pore-directing agent. MWI time and MWI power were found to have significant influence on the textural properties of synthesized m-ZrP. Microscopic analyses of the synthesized m-ZrP indicate the presence of worm like pores with spherical morphology. DRIFT analysis of pyridine adsorbed m-ZrP and NH3-TPD measurements indicate the presence of appreciable amount of Brönsted acid sites. Synthesized m-ZrP exhibits high catalytic activity towards Claisen–Schmidt condensation reaction in solvent-free conditions under microwave irradiation. The m-ZrP showed high activity towards other acid catalyzed reactions such as Friedel–Craft benzylation, Pechmann condensation and carbonyl group protection reaction, and also for the synthesis of benzo-xanthenes in solvent-free conditions under MWI. The catalytic activity of m-ZrP is substantially higher than that of conventional layered ZrP. The synthesized catalysts are re-usable for at least five times after regeneration, without losing their catalytic activity significantly.

Mesoporous zirconium phosphate catalyzed reactions: Synthesis of industrially important chemicals in solvent-free conditions

Mesoporous zirconium phosphate (m-ZrP) having high specific surface area and narrow pore size distributions is synthesized in basic medium using zirconium carbonate as source of zirconium. The concentration of phosphate in precursor solutions, as well as the calcination temperature, is found to influence the textural properties and acidity of synthesized m-ZrP significantly. Microscopic analysis indicates the presence of worm like pores with spherical morphology. The porous structure has remarkable thermal stability (up to 800 °C). DRIFT and NH 3-TPD analysis suggest the presence of reasonable amount of Lewis and Brönsted acid sites. High catalytic activity of synthesized m-ZrP is observed towards Friedel–Craft (F.C.) benzylation reaction. The effect of acid strength of catalyst, reaction time, temperature and amount of catalyst towards Friedel–Craft benzylation reaction are also studied. The m-ZrP is highly active towards other acid catalyzed reactions in solvent-free conditions. The catalytic activity of m-ZrP is much higher than that of conventional layered ZrP. The catalysts were separated easily from reaction mixture, regenerated after a simple activation step and reused at least six times without significant loss in catalytic activity.