Microwave Irradiation Conditions Research Articles

Ammonia Removal from Swine Wastewater by Microwave-Assisted Stripping

AbstractThis study detetmined optimal microwave irradiation (MI) conditions for removal of ammonia nitrogen (NH3-N) from swine wastewater. The wastewater was treated using a laboratory-scale indust...

Efficient synthesis of some pyrimidine and thiazolidine derivatives bearing quinoline scaffold under microwave irradiation

An efficient and facile approach for the synthesis of new quinoline derivatives was accomplished via reactions of 2-chloroquinoline-3-carbaldehyde with active methylene compounds, for example, 1,3-dimethylbarbituric acid, thiobarbituric acid and 2,4-dioxothiazolidine and aromatic amines through one-pot multi-component reaction (MCR) as sources of pyrimidine and thiazolidine derivatives bearing quinoline moiety. All compounds were synthesized via conventional and Microwave Irradiation conditions. The best results (short reaction times, pure products, high yield) were obtained by microwave irradiation. The synthesized derivatives were characterized by various physicochemical and spectral techniques from their analytical and spectral data.

Development of large-scale oxidative Bromination with HBr-DMSO by using a continuous-flow microwave system for the subsequent synthesis of 4-Methoxy-2-methyldiphenylamine

An efficient procedure of continuous-flow microwave reactor, for oxidative bromination with HBr (hydrogen bromide) -DMSO (dimethyl sulphoxide) in large scale is described herein. The reaction is carried out in a metal-free manner, with the use of water as solvent under microwave irradiation conditions. The productivity of this continuous step attains 60 g/min under the optimal conditions, implying a theoretical productivity of 8.6 kg/day. The reaction mixture is screened by thermal insulation accelerometer to ensure the safe process of this reaction in these conditions. 4-Bromo-3-methylanisole is further reacted with formanilide in the presence of cuprous iodide (CuI) and potassium carbonate (K2CO3) to give 4-methoxy-2-methyldiphenylamine, a common intermediate in fine chemical industry such as dye and paper chemistry, in an isolated yield of 65.2%. with more than 200 g scale.

Investigation of the Thermal Properties of Electrodes on the Film and Its Heating Behavior Induced by Microwave Irradiation in Mounting Processes

We have developed a novel microwave (MW) soldering system using a cylindrical single-mode TM110 MW cavity that spatially separates the electric fields at the top and bottom of the cavity and the magnetic field at the center of the cavity. This MW reactor system automatically detects the suitable resonance frequency and provides the optimum MW irradiation conditions in the cylindrical cavity via a power feedback loop. Furthermore, we investigated the temperature properties of electrodes by MW heating with the simulation of a magnetic field in the TM110 cavity toward the mounting of electronic components by MW heating. We also developed a short-time melting technology for solder paste on polyimide substrate using MW heating and succeeded in mounting a temperature sensor using the novel MW heating system without damaging the electronic components, electronic circuits, and the substrate.

Microwave assisted freezing part 2: Impact of microwave energy and duty cycle on ice crystal size distribution

Among innovative freezing processes, electromagnetic wave assistance during freezing has received great attention in recent years. The literature provides interesting studies indicating that smaller ice crystals may be obtained during freezing with the assistance of microwaves. In the companion paper, we designed a laboratory scale prototype to perform experiments of this type in well controlled conditions at 2.45 GHz. In the current study, we performed freezing experiments using this prototype and developed a protocol to measure ice crystal sizes using X-ray micro-tomography. The methodology was first validated by measuring ice crystal distribution in unidirectional conventional freezing. Then several microwave assisted freezing modalities were studied. Experiments were conducted with pulsed and continuously applied microwaves. The impact of microwave irradiation time was studied at a constant incident microwave power, and then at constant energy supplied to the system. We observed a significant reduction of up to 25% in ice crystal size when microwave assistance was used during freezing with both pulsed and continuously applied microwaves. These observations tend to disconfirm the hypothesis in the literature according to which ice crystal size reduction is due to temperature oscillations. The only remaining hypothesis in the literature is that ice crystal size reduction may be due to the perturbation of the H-bond network in water, which could be a precursor to crystalline structure. It appeared that at constant incident microwave power, the increase in irradiation time tended to decrease ice crystal size. No significant difference in ice crystal size reduction was observed for a constant energy supplied to the system. The amount of energy supplied by microwaves seems to be a factor influencing ice crystal size.Industrial relevanceMicrowave assisted freezing is an emerging process which permits reducing ice crystal size, and thus improving frozen product quality. The measurement of ice crystals in samples frozen in controlled conditions of both freezing and microwave irradiation allows studying the main parameters that induce the reduction of their size. Better understanding of the relevant factors influencing nucleation and/or crystal growth can help to optimize the process.

A novel nanomagnetic solid acid catalyst for the synthesis of new functionalized bis‐coumarin derivatives under microwave irradiations in green conditions

In this study, a novel, green, environmentally friendly and magnetically heterogeneous catalyst based on the immobilization of sulfosalicylic acid onto Fe3O4nanoparticles (Fe3O4@sulfosalicylic acid MNPs) is reported. The bis‐coumarin analogs were synthesized in high yield using the reaction of 1 equivalent of aryl aldehydes with 2 equivalents of 4‐hydroxycoumarin in water under microwave irradiation conditions. Scanning electron microscopy, transmission electron microscopy, energy‐dispersive X‐ray spectroscopy, X‐ray diffraction, thermogravimetric analysis, dynamic light scattering, vibrating sample magnetometry, Fourier transform infrared spectroscopy, UV–visible absorption, and Brunauer‐Emmett‐Teller (BET) techniques confirmed the successful synthesis of the catalyst. The main attractive characteristics of the presented green protocol are very short reaction times (10–15 min), excellent yields, and the avoidance of hazardous or toxic reagent and solvents. Thermal durability, easy separation, and high reusability are important advantages of the new catalyst in comparison to other catalysts.

Could Microwave Irradiation Cause Misfolding of Peptides?

Microwaves have been experimentally shown to affect the folding dynamics of peptides and proteins. Using molecular dynamics, we performed all-atom simulations of a model β-peptide in aqueous solution where individual degrees of freedom of solvent molecules were decoupled to allow for investigation at non-equilibrium microwave-irradiated conditions. An elevated rotational temperature of the water medium was found to significantly affect the conformation of the peptide due to the weakened hydrogen-bonding interactions with the surrounding solvent molecules. Cluster analysis revealed that microwave irradiation can indeed act as a promoter in the formation of new misfolded peptide structures of the hairpin type, which are generally associated with the onset of several neurodegenerative disorders such as Alzheimer’s, Parkinson’s, Huntington’s, and Creutzfeldt–Jakob diseases as well as certain cancer types such as amyloidosis.

New Dual-Functional and Reusable Bimetallic Y2ZnO4 Nanocatalyst for Organic Transformation under Microwave/Green Conditions.

A novel bimetallic and reusable Y2ZnO4 nanocatalyst was synthesized by a simple coprecipitation method. The prepared nanocatalyst exhibited dual catalytic activity and was characterized using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), energy-dispersive X-ray spectroscopy (EDX), and scanning electron microscopy (SEM). The average crystallite and grain sizes were found to be 17 ± 1 and 10 ± 2 nm, respectively. On the one hand, the catalytic activity of the nanocatalyst was studied for the Knoevenagel condensation reaction of aromatic aldehydes with active methylene compounds, such as ethyl cyanoacetate and malononitrile, under microwave irradiation and solvent-free conditions. On the other hand, the nanoparticles also showed faster photocatalytic activity against methyl orange (MO) compared to other dyes. The nanocatalyst was easily recoverable by a simple filtration method and was recycled without any significant loss of catalytic activity. The advantages of this nanocatalyst were a simple workup procedure, high reaction yields, solvent-free conditions, reusability, and a short reaction time under green reaction conditions.

Enriched graphitic N dopants of carbon dots as F cores mediate photothermal conversion in the NIR-II window with high efficiency

We have developed the rapid synthesis of NIR–II–responsive carbon dots (NIR–II–CDs) under microwave irradiation conditions. A close correlation between the photothermal effects and graphitic N doping level is well established by two observed effects: 1) absorbance at 808 and 1064 nm was consistently proportional to the graphitic N content; 2) the photothermal conversion efficiency remarkably increased with the graphitic N content. We further revealed a distinct photothermal conversion mechanism in the NIR–II–CDs, where doped graphitic N sites as paramagnetic F centers can mediate the highly efficient NIR absorption and photothermal conversion. Importantly, readily derived NIR–II–CDs with a graphitic N doping level as high as 4.30 at.% showed ultrahigh photothermal conversion efficiency of 81.3% in the NIR-II window. Using NIR–II–CDs or their hybrid liposomal formula as single PTT or imaging-guided PCT agents, complete tumor ablation without recurrence was realized under the 1064-nm laser irradiation at low laser power densities even in the presence of the breast tissue with a thickness larger than 10 mm. Our results suggest that the photothermal properties of biocompatible CDs can be regulated in the extended NIR regions by doping a high concentration of graphitic N defects as color centers for tumor treatment with minimized side effects.

Synthesis, cytotoxic assessment, and molecular docking studies of 2,6-diaryl-substituted pyridine and 3,4- dihydropyrimidine-2(1H)-one scaffolds.

Cancer is one of the main global health problems. In order to develop novel antitumor agents, we synthesized 3,4-dihydropyrimidine-2(1H)-one (DHPM) and 2,6-diaryl-substituted pyridine derivatives as potential antitumor structures and evaluated their cytotoxic effects against several cancer cell lines. An easy and convenient method is reported for the synthesis of these derivatives, employing cobalt ferrite (CoFe 2 O 4 @SiO 2 -SO 3 H) magnetic nanoparticles under microwave irradiation and solvent-free conditions. The structural characteristics of the prepared nanocatalyst were investigated by FTIR, XRD, SEM, and TGA techniques. In vitro cytotoxic effects of the synthesized products were assessed against the human breast adenocarcinoma cell line (MCF-7), gastric adenocarcinoma (AGS), and human embryonic kidney (HEK293) cells via MTT assay. The results indicated that compound 4r (DHPM derivative) was the most toxic molecule against the MCF-7 cell line (IC 50 of 0.17 μg/mL). Moreover, compounds 4j and 4r (DHPM derivatives) showed excellent cytotoxic activities against the AGS cell line, with an IC 50 of 4.90 and 4.97 μg/mL, respectively. Although they are pyridine derivatives, compounds 5g and 5m were more active against the MCF-7 cell line. Results showed that the candidate compounds exhibited low cytotoxicity against HEK293 cells. The kinesin Eg5 inhibitory potential of the candidate compounds was evaluated by molecular docking. The docking results showed that, among the pyridine derivatives, compound 5m had the most free energy of binding (–9.52 kcal/mol) and lowest Ki (0.105 μM), and among the pyrimidine derivatives, compound 4r had the most free energy of binding (–7.67 kcal/mol) and lowest Ki (2.39 μM). Ligand-enzyme affinity maps showed that compounds 4r and 5m had the potential to interact with the Eg5 binding site via H-bond interactions to GLU116 and GLY117 residues. The results of our study strongly suggest that DHPM and pyridine derivatives inhibit important tumorigenic features of breast and gastric cancer cells. Our results may be helpful in the further design of DHPMs and pyridine derivatives as potential anticancer agents.

In vitro anticancer activity of pyrano[3, 2-c]chromene derivatives with both cell cycle arrest and apoptosis induction

A series of 2-amino-4-aryl-5-oxo-4,5-dihydropyrano[3,2-c]chromene-3-carbonitrile (4a–m) were synthesized via a one-pot three component condensation reaction between 4-hydroxy-2H-chromen-2-one, various aryl aldehydes and malononitrile in the presence of piperidine as a catalyst in ethanol under microwave irradiation conditions, with good to excellent yields. The structure elucidations of all the synthesized compounds were accomplished by spectral data, IR, 1H NMR, 13C NMR, MS, and elemental analyses. The targeted compounds were assessed for their in vitro anticancer activity against mammary gland breast cancer cell line (MCF-7), human colon cancer (HCT-116), and liver cancer (HepG-2) by using sulphorhodamine B assay (SRB) method, while doxorubicin, was utilized as standard reference drug. The cancer cells were treated with the synthesized compounds at differentiable dosages, and cell viability was determined. Compounds 4e, 4f, and 4m exhibited excellent antitumor activity versus all cancer cell lines with IC50 values ranging from 0.2 to 1.7 μM. The cell cycle arrest behavior of compounds 4e, 4f, and 4m was investigated. The results illustrated that the potent cytotoxic compounds 4e, 4f, and 4m induce cell cycle arrest at the G2/M phases and trigger apoptosis in the different tested cancer cells. Finally, the structure activity relationship (SAR) survey highlighted the antitumor activity of the new molecules that was remarkably influenced by the hydrophilicity of certain substituents at certain positions.

Green catalyst-free one-pot synthesis of novel tetrahydropyridine-3-carboxamides by microwave-assisted approach

A clean, facile and catalyst-free four-component domino reaction of aromatic aldehyde, ethyl cyanoacetate, acetoacetanilide and ammonium acetate in ethanol under microwave irradiation (MWI) conditions is described. Eleven novel and diverse tetrahydropyridine-3-carboxamide derivatives were synthesized in excellent yields (91–97%) using this green protocol. The significant benefits of this method are simple handling, ethanol as solvent, catalyst-free reaction under mild conditions, short reaction times (<10 min) and excellent product yields. Easy workup procedure and simple purification technique of the target molecules evade column chromatography. Novel tetrahydropyridine-3-carboxamide derivatives were synthesized under the microwave irradiation (MWI) method in short reaction time (<10 min). All the synthesized compounds confirmed by various spectroscopic techniques such as 1H NMR, 13C NMR, 15N NMR and HRMS. Ethanol as a solvent, easy workup procedure and simple handling are the benefit of green protocol.

Unusual Transformations of Cyclic Allenes with an Enamine Moiety into Complex Frameworks

The thermolysis reactions of benzoazacyclodecatrienes under microwave irradiation conditions in toluene at 150 °C afforded complex azabenzo[a]cyclopropa[cd]azulene and (epiminomethano)cyclopenta[a]indene frameworks. Cyclopropanes were established as intermediates of the ultimate thermolysis products.

Green one-pot synthesis of N-bisphosphonates as antimicrobial and antioxidant agents

A straightforward and greener approach has been developed for the synthesis of novel aminomethylene bisphosphonates by one-pot reaction of diverse aryl/heteroaryl amines with dialkyl phosphite and triethyl orthoformate using CuO nanoparticles as catalyst under microwave irradiation and solvent-free conditions. This is an ecofriendly synthetic approach for swift access to a library of diverse aminomethylene bisphosphonates. All the synthesized new compounds were evaluated for their antimicrobial activity by disc diffusion method and antioxidant activity by DPPH, H2O2, and NO methods. The title compounds exhibited significant antioxidant and considerable antimicrobial activities.

Eco‐friendly synthesis of novel pyrimidine derivatives as potential anticancer agents

AbstractHerein, a rapid and highly efficient method for the synthesis of a new series of pyrimidine derivatives was demonstrated. The strategy was emanated from the reaction of hydrazinyl pyrimidine derivative (1) with different electrophilic species such as ethyl acetoacetate, ethyl 4,4,4‐trifluoro acetoacetate, and phenyl isothiocyanate following cyclocondensation mechanism to afford the corresponding derivatives (2‐6). Furthermore, condensation of hydrazine derivative (1) with different carbonyl compounds via conventional heating and microwave irradiation conditions was employed as a source of Schiff base derivatives bearing pyrimidine moiety (7‐12). The structural features of all newly synthesized compounds were characterized by elemental and spectroscopic evidences. Some of the synthesized compounds were evaluated for in vitro cytotoxicity. The preliminary screening results showed that most of the tested compounds have moderate cytotoxic activity against HepG2 and HCT‐116 cell lines. Finally, a molecular docking study was conducted to reveal the probable interaction with the thymidylate synthase enzyme.

Synthesis of bioactive quinazolin-4(3H)-one derivatives via microwave activation tailored by phase-transfer catalysis.

A series of nine new 2,3-disubstituted 4(3H)-quinazolin-4-one derivatives was furnished starting from the 2-propyl-4(3H)-quinazo-line-4-one (2). The reinvestigation of the key starting quinazolinone 2 was performed under microwave irradiation (MW) and solvent-free conditions. Combination of MW and phase-transfer catalysis using tetrabutylammonium benzoate (TBAB) as a novel neutral ionic catalyst was used for carrying out N-alkylation and condensation reactions of compound 2 as a simple, efficient and eco-friendly technique. The structure of the synthesized compounds was elucidated using different spectral and chemical analyses. In vitro antimicrobial activity of the compounds was investigated against four bacterial and two fungal strains; very modest activity was achieved. Some of the synthesized compounds were screened for their antitumor activity against different human tumor cell lines. The screened compounds exhibited a significant antitumor activity on some of the cancer cell lines, melanoma (SK-MEL-2), ovarian cancer (IGROV1), renal cancer (TK-10), prostate cancer (PC-3), breast cancer (MCF7) and colon cancer (HT29). The most active, even more active than the reference 5-fluorouracil, were found to be ethyl 4-[(4-oxo-2-propylquinazolin-3(4H)-yl)methyl]benzoate (3c), 3-{2-[6-(pyrrolidin-1-yl-sulfonyl)-1,2,3,4-tetrahydroquinoline]-2-oxoethyl}-2-propylquinazolin--4(3H)-one (3e), N'-[(E)-(2H-1,3-benzodioxo-5-yl)methylidene]-2-(4-oxo-2-propylquinazolin-3(4H)-yl)acetohydrazide (10a), N'-[(E)-(4-hydroxyphenyl)methylidene]-2-(4-oxo-2-propylquinazo-lin-3(4H) -yl)acetohydrazide (10b) and N'-[(E)-(4-nitrophenyl)methyl idene]-2-(4-oxo-2-propylquinazolin-3(4H)-yl)acetohydrazide (10c).

TMSOTf-catalyzed synthesis of substituted quinazolines using hexamethyldisilazane as a nitrogen source under neat and microwave irradiation conditions.

In this article, we report an efficient and mild synthetic route for the construction of substituted quinazolines from functionalized 2-aminobenzophenones with various benzaldehydes using cat. TMSOTf and hexamethyldisilazane (HMDS) under neat, metal-free and microwave irradiation conditions in which gaseous ammonia was formed in situ. This synthetic protocol provided the desired quinazolines with a broad substrate scope in good to excellent yields. Some structures were confirmed by X-ray single-crystal diffraction analysis.

The mechanism of promoter-induced zeolite nanosheet crystallization under hydrothermal and microwave irradiation conditions

The mechanism of MFI zeolite nanosheet formation was established under accelerated conditions using perchlorate ions and fresh zeolite seeds as promoters.

Microwave-assisted functionalization of carbon nanohorns with oligothiophene units with SERS activity.

Carbon nanohorns have been functionalized with oligothiophene units via the 1,3-dipolar cycloaddition reaction under microwave irradiation and solvent-free conditions. A dramatic Raman enhancement was found for one of the synthesized derivatives. Experimental and in silico studies helped to understand the enhancement, attributed to the modification of electromagnetic fields upon functionalization at the tip of the nanostructures.

Microwave-assisted synthesis, biological evaluation and molecular docking studies of new coumarin-based 1,2,3-triazoles.

Coumarin-based 1,4-disubstituted 1,2,3-triazole derivatives were synthesized using a highly efficient, eco-friendly protocol via a copper(i)-catalyzed click reaction between various substituted arylazides and terminal alkynes. The synthetic route was easy to access and gave excellent yields under microwave irradiation conditions compared to the conventional heating route. The structures of all the compounds were characterized by IR, 1H NMR, 13C NMR spectroscopy and mass spectrometry. All the synthesized compounds were screened for their in vitro antimicrobial, antioxidant and anti-inflammatory activities; among all compounds, 8a, 8j, 8k and 8l exhibited better results with respect to standard drugs. Furthermore, molecular docking studies have been carried out with PDB IDs 2VCX (anti-inflammatory), 3VXI (antioxidant), 4GEE (antimicrobial) and 2XFH (antifungal) using the Glide module of the Schrödinger suite. The final compounds 8d, 8e, 8h, and 8k showed the highest hydrogen bond interactions with His-88 and Val-191 proteins and with water in all the proteins.