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Microwave-Mediated Chemistry

A special issue of Molecules (ISSN 1420-3049). This special issue belongs to the section "Organic Chemistry".

Deadline for manuscript submissions: closed (31 October 2019) | Viewed by 41327

Special Issue Editor

Department of Chemistry, University of Sussex, Sussex, UK
Interests: palladium catalysis; medicinal chemistry; heterocycle synthesis; cancer; p53
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Special Issue Information

Dear Colleagues,

Microwave-mediated chemistry continues to have an impact on chemical synthesis, scale-up, medicinal chemistry, catalysis, material science and many other areas of science. Often, yields are improved and processes can be carried out in minutes compared to their thermal counterparts. Many processes can be carried out in batches or can be solvent-free.

It is a great pleasure to invite you to participate in show-casing your work in microwave-mediated chemistry.

Prof. Dr. John Spencer
Guest Editor

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Keywords

  • microwaves
  • catalysis
  • medicinal chemistry
  • flow chemistry
  • materials science

Published Papers (11 papers)

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Research

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39 pages, 8607 KiB  
Article
Innovative Three-Step Microwave-Promoted Synthesis of N-Propargyltetrahydroquinoline and 1,2,3-Triazole Derivatives as a Potential Factor Xa (FXa) Inhibitors: Drug Design, Synthesis, and Biological Evaluation
by Fabián Santana-Romo, Carlos F. Lagos, Yorley Duarte, Francisco Castillo, Yanina Moglie, Miguel A. Maestro, Nitin Charbe and Flavia C. Zacconi
Molecules 2020, 25(3), 491; https://doi.org/10.3390/molecules25030491 - 23 Jan 2020
Cited by 20 | Viewed by 6172
Abstract
The coagulation cascade is the process of the conversion of soluble fibrinogen to insoluble fibrin that terminates in production of a clot. Factor Xa (FXa) is a serine protease involved in the blood coagulation cascade. Moreover, FXa plays a vital role in the [...] Read more.
The coagulation cascade is the process of the conversion of soluble fibrinogen to insoluble fibrin that terminates in production of a clot. Factor Xa (FXa) is a serine protease involved in the blood coagulation cascade. Moreover, FXa plays a vital role in the enzymatic sequence which ends with the thrombus production. Thrombosis is a common causal pathology for three widespread cardiovascular syndromes: acute coronary syndrome (ACS), venous thromboembolism (VTE), and strokes. In this research a series of N-propargyltetrahydroquinoline and 1,2,3-triazole derivatives as a potential factor Xa (FXa) inhibitor were designed, synthesized, and evaluated for their FXa inhibitor activity, cytotoxicity activity and coagulation parameters. Rational design for the desired novel molecules was performed through protein-ligand complexes selection and ligand clustering. The microwave-assisted synthetic strategy of selected compounds was carried out by using Ullmann-Goldberg, N-propargylation, Mannich addition, Friedel-Crafts, and 1,3-dipolar cycloaddition type reactions under microwave irradiation. The microwave methodology proved to be an efficient way to obtain all novel compounds in high yields (73–93%). Furthermore, a thermochemical analysis, optimization and reactivity indexes such as electronic chemical potential (µ), chemical hardness (η), and electrophilicity (ω) were performed to understand the relationship between the structure and the energetic behavior of all the series. Then, in vitro analysis showed that compounds 27, 2931, and 34 exhibited inhibitory activity against FXa and the corresponding half maximal inhibitory concentration (IC50) values were calculated. Next, a cell viability assay in HEK293 and HepG2 cell lines, and coagulation parameters (anti FXa, Prothrombin time (PT), activated Partial Thromboplastin Time (aPTT)) of the most active novel molecules were performed to determine the corresponding cytotoxicity and possible action on clotting pathways. The obtained results suggest that compounds 27 and 29 inhibited FXa targeting through coagulation factors in the intrinsic and extrinsic pathways. However, compound 34 may target coagulation FXa mainly by the extrinsic and common pathway. Interestingly, the most active compounds in relation to the inhibition activity against FXa and coagulation parameters did not show toxicity at the performed coagulation assay concentrations. Finally, docking studies confirmed the preferential binding mode of N-propargyltetrahydroquinoline and 1,2,3-triazole derivatives inside the active site of FXa. Full article
(This article belongs to the Special Issue Microwave-Mediated Chemistry)
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10 pages, 10186 KiB  
Article
One-Pot Two-Step Synthesis of 2-Aryl benzimidazole N-oxides Using Microwave Heating as a Tool
by Fabrizio Politano, Ana K. Gran-Magano and Nicholas E. Leadbeater
Molecules 2019, 24(20), 3639; https://doi.org/10.3390/molecules24203639 - 09 Oct 2019
Cited by 4 | Viewed by 4185
Abstract
A methodology is reported for the preparation of 2-aryl-benzimidazole-3-oxide derivatives. By means of a one-pot two-step protocol, a library of 42 new compounds has been prepared. Reactions were performed in a total time of 40 min using microwave heating as a tool. A [...] Read more.
A methodology is reported for the preparation of 2-aryl-benzimidazole-3-oxide derivatives. By means of a one-pot two-step protocol, a library of 42 new compounds has been prepared. Reactions were performed in a total time of 40 min using microwave heating as a tool. A streamlined work-up process was also developed, allowing for facile isolation of the products. The methodology offers a more sustainable approach than previous routes, with only water and ethanol being used as solvents, and the products being isolated by means of a simple filtration without the need for any further purification. Full article
(This article belongs to the Special Issue Microwave-Mediated Chemistry)
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13 pages, 3700 KiB  
Article
Comparison of Engine Performance between Nano- and Microemulsions of Solketal Droplets Dispersed in Diesel Assisted by Microwave Irradiation
by Cherng-Yuan Lin and Shih-Ming Tsai
Molecules 2019, 24(19), 3497; https://doi.org/10.3390/molecules24193497 - 26 Sep 2019
Cited by 4 | Viewed by 2141
Abstract
As a derivative product of bio-glycerol, this study first uses solketal as a combustion improver for enhancing diesel engine characteristics. The emulsions of nanometer- and micrometer-sized droplets of solketal, which disperse evenly in the ultra-low sulfur diesel (ULSD), are formed by the effects [...] Read more.
As a derivative product of bio-glycerol, this study first uses solketal as a combustion improver for enhancing diesel engine characteristics. The emulsions of nanometer- and micrometer-sized droplets of solketal, which disperse evenly in the ultra-low sulfur diesel (ULSD), are formed by the effects of microwave irradiation. The performance of diesel engine fueled with the nanoemulsion of ULSD with scattered solketal droplets is analyzed and compared to that with the microemulsion. The experimental results show that the nanoemulsions can form when over 15 wt. % surfactant mixtures of Span 80 and Tween 80 and less than 5 wt. % solketal are mixed and emulsified with the remaining ULSD content, which acts as the continuous phase of the emulsions. The nanoemulsions are observed to have significantly lower brake-specific fuel consumption (bsfc) and higher fuel conversion efficiency and exhaust gas temperature than those of the microemulsions and the neat ULSD. However, the bsfc of the nanoemulsions increases with greater engine speed and gradually approaches those of the latter two test fuels. In addition, the dispersed solketal droplet sizes are mostly concentrated around 127 nm with peak intensity of 12.65% in the nanoemulsions. The microwave-assisted formation used in this study is found to successfully produce the nanoemulsions in which all of the dispersed droplet sizes are much smaller than 1000 nm. Full article
(This article belongs to the Special Issue Microwave-Mediated Chemistry)
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14 pages, 4283 KiB  
Article
Template-Assisted Synthesis of Luminescent Carbon Nanofibers from Beverage-Related Precursors by Microwave Heating
by Clara Deeney, Eoin P. McKiernan, Samir A. Belhout, Brian J. Rodriguez, Gareth Redmond and Susan J. Quinn
Molecules 2019, 24(8), 1455; https://doi.org/10.3390/molecules24081455 - 12 Apr 2019
Cited by 7 | Viewed by 3649
Abstract
Luminescent carbon nanomaterials are important materials for sensing, imaging, and display technologies. This work describes the use of microwave heating for the template-assisted preparation of luminescent carbon nanofibers (CNFs) from the reaction of a range of beverage-related precursors with the nitrogen-rich polyethyleneimine. Highly [...] Read more.
Luminescent carbon nanomaterials are important materials for sensing, imaging, and display technologies. This work describes the use of microwave heating for the template-assisted preparation of luminescent carbon nanofibers (CNFs) from the reaction of a range of beverage-related precursors with the nitrogen-rich polyethyleneimine. Highly luminescent robust carbon fibers that were 10 to 30 μm in length and had a diameter of 200 nm were obtained under moderate conditions of temperature (250–260 °C) and a short reaction time (6 min). The high aspect ratio fibers showed wavelength-dependent emission that can be readily imaged using epifluorescence. The development of these multi-emissive one-dimensional (1D) carbon nanomaterials offers potential for a range of applications. Full article
(This article belongs to the Special Issue Microwave-Mediated Chemistry)
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12 pages, 775 KiB  
Article
Green Methodologies for Copper(I)-Catalyzed Azide-Alkyne Cycloadditions: A Comparative Study
by Marissa Trujillo, Clayton Hull-Crew, Andrew Outlaw, Kevin Stewart, Loren Taylor, Laura George, Allison Duensing, Breanna Tracey and Allen Schoffstall
Molecules 2019, 24(5), 973; https://doi.org/10.3390/molecules24050973 - 10 Mar 2019
Cited by 13 | Viewed by 3550
Abstract
Successful copper(I)-catalyzed azide-alkyne cycloaddition (CuAAC) reactions may be achieved by several methods. In this paper, four synthetic protocols were performed for direct comparison of time required for the synthesis, yield, and purity of the 1H-1,2,3-triazole products. The methods with Cu(I) catalysts [...] Read more.
Successful copper(I)-catalyzed azide-alkyne cycloaddition (CuAAC) reactions may be achieved by several methods. In this paper, four synthetic protocols were performed for direct comparison of time required for the synthesis, yield, and purity of the 1H-1,2,3-triazole products. The methods with Cu(I) catalysts were conventional, microwave heating, solvent-free, and a method using glycerol solvent. The compounds synthesized in this paper were known non-fluorinated triazoles and new fluorinated triazoles. The results lead to the conclusion that the microwave method should be strongly considered for CuAAC syntheses. Full article
(This article belongs to the Special Issue Microwave-Mediated Chemistry)
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14 pages, 2850 KiB  
Article
Microwave-Assisted Synthesis of Mono- and Disubstituted 4-Hydroxyacetophenone Derivatives via Mannich Reaction: Synthesis, XRD and HS-Analysis
by Ghadah Aljohani, Musa A. Said, Dieter Lentz, Norazah Basar, Arwa Albar, Shaya Y. Alraqa and Adeeb Al-Sheikh Ali
Molecules 2019, 24(3), 590; https://doi.org/10.3390/molecules24030590 - 07 Feb 2019
Cited by 9 | Viewed by 3407
Abstract
An efficient microwave-assisted one-step synthetic route toward Mannich bases is developed from 4-hydroxyacetophenone and different secondary amines in quantitative yields, via a regioselective substitution reaction. The reaction takes a short time and is non-catalyzed and reproducible on a gram scale. The environmentally benign [...] Read more.
An efficient microwave-assisted one-step synthetic route toward Mannich bases is developed from 4-hydroxyacetophenone and different secondary amines in quantitative yields, via a regioselective substitution reaction. The reaction takes a short time and is non-catalyzed and reproducible on a gram scale. The environmentally benign methodology provides a novel alternative, to the conventional methodologies, for the synthesis of mono- and disubstituted Mannich bases of 4-hydroxyacetophenone. All compounds were well-characterized by FT-IR, 1H NMR, 13C NMR, and mass spectrometry. The structures of 1-{4-hydroxy-3-[(morpholin-4-yl)methyl]phenyl}ethan-1-one (2a) and 1-{4-hydroxy-3-[(pyrrolidin-1-yl)methyl]phenyl}ethan-1-one (3a) were determined by single crystal X-ray crystallography. Compound 2a and 3a crystallize in monoclinic, P21/n, and orthorhombic, Pbca, respectively. The most characteristic features of the molecular structure of 2a is that the morpholine fragment adopts a chair conformation with strong intramolecular hydrogen bonding. Compound 3a exhibits intermolecular hydrogen bonding, too. Furthermore, the computed Hirshfeld surface analysis confirms H-bonds and π–π stack interactions obtained by XRD packing analyses. Full article
(This article belongs to the Special Issue Microwave-Mediated Chemistry)
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15 pages, 1886 KiB  
Article
Microwave-Assisted Stereoselective Heterocyclization to Novel Ring d-fused Arylpyrazolines in the Estrone Series
by Gergő Mótyán, Barnabás Molnár, János Wölfling and Éva Frank
Molecules 2019, 24(3), 569; https://doi.org/10.3390/molecules24030569 - 04 Feb 2019
Cited by 7 | Viewed by 2549
Abstract
Microwave-assisted syntheses of novel ring d-condensed 2-pyrazolines in the estrone series were efficiently carried out from steroidal α,β-enones and hydrazine derivatives. The ring-closure reaction of 16-benzylidene estrone 3-methyl ether with hydrazine in acetic acid resulted in a 2:1 diastereomeric mixture of two [...] Read more.
Microwave-assisted syntheses of novel ring d-condensed 2-pyrazolines in the estrone series were efficiently carried out from steroidal α,β-enones and hydrazine derivatives. The ring-closure reaction of 16-benzylidene estrone 3-methyl ether with hydrazine in acetic acid resulted in a 2:1 diastereomeric mixture of two 16,17-cis fused pyrazolines, which is contrary to the former literature data for both stereoselectivity and product structure. However, the cyclization reactions of a mestranol-derived unsaturated ketone with different arylhydrazines in acidic ethanol furnished the heterocyclic products in good to excellent yields independently of the substituents present on the aromatic ring of the reagents applied. The MW conditions also permitted the ring-closure reaction with p-nitrophenylhydrazine which is unfavorable under conventional heating. Moreover, the transformations led to the heterocyclic compounds stereoselectively with a 16α,17α-cis ring junction without being susceptible to spontaneous and promoted oxidation to pyrazoles. Full article
(This article belongs to the Special Issue Microwave-Mediated Chemistry)
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10 pages, 5837 KiB  
Article
Synthesis of Chromium Carbide Nanopowders by Microwave Heating and Their Composition and Microstructure Change under Gamma Ray Irradiation
by Kai Jin, Yuanbo Jia, Zhiwei Zhao, Weiqiang Song, Shun Wang and Chunlong Guan
Molecules 2019, 24(1), 16; https://doi.org/10.3390/molecules24010016 - 20 Dec 2018
Cited by 7 | Viewed by 3233
Abstract
Chromium carbide nanopowders were synthesized by mechanical alloying-assisted microwave heating. The effect of gamma irradiation on phase composition and microstructure of chromium carbide nanopowders synthesized by the microwave heating method was analyzed. The samples were characterized by X-ray diffractometry (XRD), X-ray photoelectron spectroscopy [...] Read more.
Chromium carbide nanopowders were synthesized by mechanical alloying-assisted microwave heating. The effect of gamma irradiation on phase composition and microstructure of chromium carbide nanopowders synthesized by the microwave heating method was analyzed. The samples were characterized by X-ray diffractometry (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and high-resolution transmission electron microscopy (HRTEM) techniques. The results showed that well-dispersed chromium carbide nanopowders can be synthesized by maintaining the temperature at 1000 °C for 1 h. Gamma ray irradiation had an important effect on the microstructure of chromium carbide nanopowders. The interplanar spacings of chromium carbide (110) crystal faces before and after gamma ray irradiation were 0.3725 nm and 0.3824 nm, respectively. The crystal structure of chromium carbide was changed by gamma ray irradiation. Gamma ray irradiation can also increase the binding energy of chromium carbide, which is beneficial to improve the thermal stability and mechanical properties of chromium carbide at high temperature. Full article
(This article belongs to the Special Issue Microwave-Mediated Chemistry)
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13 pages, 909 KiB  
Article
Microwave Irradiation Assists the Synthesis of a Novel Series of bis-Arm s-Triazine Oxy-Schiff Base and Oxybenzylidene Barbiturate Derivatives
by Kholood A. Dahlous, Zainab Almarhoon, Ahmed-Yacine Badjah-Hadj-Ahmed, Zeid A. AL Othman and Ayman El-Faham
Molecules 2018, 23(11), 2976; https://doi.org/10.3390/molecules23112976 - 14 Nov 2018
Cited by 2 | Viewed by 3751
Abstract
A novel series of s-triazines incorporating 4-hydroxybenzaldehyde and 4-hydroxy-3-methoxybenzaldehyde was prepared and fully characterized. The reaction was carried out via stepwise nucleophilic aromatic substitution of chlorine atoms in cyanuric chloride. The first chlorine was substituted by different amines (morpholine, piperidine, or diethylamine) [...] Read more.
A novel series of s-triazines incorporating 4-hydroxybenzaldehyde and 4-hydroxy-3-methoxybenzaldehyde was prepared and fully characterized. The reaction was carried out via stepwise nucleophilic aromatic substitution of chlorine atoms in cyanuric chloride. The first chlorine was substituted by different amines (morpholine, piperidine, or diethylamine) to afford 2,4-dichloro-6-substituted-1,3,5-triazine. The second and third chlorines were substituted by benzaldehyde derivatives in the presence of Na2CO3 as a HCl scavenger to afford the target products: s-triazine oxyaldehyde derivatives (dipodal). The dipodal derivatives were reacted with acid hydrazide, hydralazine, barbituric, or thiobarbituric acid derivatives using conventional heating or microwave irradiation to afford the di-arm s-triazine oxy-Schiff base and oxybenzylidene barbiturate derivatives in good yields. Microwave irradiation done in less solvent afforded the target product in less reaction time with good yield and purity. These types of derivatives might have special interest in coordination and medicinal chemistry. Full article
(This article belongs to the Special Issue Microwave-Mediated Chemistry)
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10 pages, 2122 KiB  
Article
Microwave-Assisted Expeditious Synthesis of 2-Alkyl-2-(N-arylsulfonylindol-3-yl)-3-N-acyl-5-aryl-1,3,4-oxadiazolines Catalyzed by HgCl2 under Solvent-Free Conditions as Potential Anti-HIV-1 Agents
by Zhiping Che, Yuee Tian, Shengming Liu, Jia Jiang, Mei Hu and Genqiang Chen
Molecules 2018, 23(11), 2936; https://doi.org/10.3390/molecules23112936 - 10 Nov 2018
Cited by 6 | Viewed by 2179
Abstract
A series of 2-alkyl-2-(N-arylsulfonylindol-3-yl)-3-N-acyl-5-aryl-1,3,4-oxadiazolines were expeditious prepared under microwave-assisted, catalyzed by HgCl2 and solvent-free conditions. This method has the advantage of low catalyst loading and recovering catalyst, ease reaction and repaid reaction times, easy separation products and excellent [...] Read more.
A series of 2-alkyl-2-(N-arylsulfonylindol-3-yl)-3-N-acyl-5-aryl-1,3,4-oxadiazolines were expeditious prepared under microwave-assisted, catalyzed by HgCl2 and solvent-free conditions. This method has the advantage of low catalyst loading and recovering catalyst, ease reaction and repaid reaction times, easy separation products and excellent yields, and more conducive to the large-scale synthesis products. Furthermore, compounds 3s, 3y, 3a′, 3b′, 3f′, 3i′, 3q′, and 3r′ exhibited more potent anti-HIV-1 activity with EC50 values of 3.35, 6.12, 3.63, 9.54, 1.79, 0.51, 3.00, and 4.01 μg/mL, and TI values of 32.66, >32.68, 31.22, 13.94, 24.27, 39.59, 26.01, and 24.51, respectively. Especially compound 3i′ displayed the highest anti-HIV-1 activity with TI values of 39.59. Full article
(This article belongs to the Special Issue Microwave-Mediated Chemistry)
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Review

Jump to: Research

35 pages, 7687 KiB  
Review
Microwave-Driven Synthesis of Iron-Oxide Nanoparticles for Molecular Imaging
by Irene Fernández-Barahona, Maria Muñoz-Hernando and Fernando Herranz
Molecules 2019, 24(7), 1224; https://doi.org/10.3390/molecules24071224 - 28 Mar 2019
Cited by 29 | Viewed by 5754
Abstract
Here, we present a comprehensive review on the use of microwave chemistry for the synthesis of iron-oxide nanoparticles focused on molecular imaging. We provide a brief introduction on molecular imaging, the applications of iron oxide in biomedicine, and traditional methods for the synthesis [...] Read more.
Here, we present a comprehensive review on the use of microwave chemistry for the synthesis of iron-oxide nanoparticles focused on molecular imaging. We provide a brief introduction on molecular imaging, the applications of iron oxide in biomedicine, and traditional methods for the synthesis of these nanoparticles. The review then focuses on the different examples published where the use of microwaves is key for the production of nanoparticles. We study how the different parameters modulate nanoparticle properties, particularly for imaging applications. Finally, we explore principal applications in imaging of microwave-produced iron-oxide nanoparticles. Full article
(This article belongs to the Special Issue Microwave-Mediated Chemistry)
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