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Microwave-Assisted Organic Synthesis

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

Deadline for manuscript submissions: closed (15 October 2015) | Viewed by 36711

Special Issue Editors


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Guest Editor
Microwave Technologies Consulting, Lyon, France
Interests: microwaves; scale-up; microwave plasma; microwave-assisted synthesis; microwave drying; microwave-assisted extraction; sterilization; pasteurization
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Guest Editor
Formerly Head, Department of Organic Chemistry (FS), University of Mons-UMONS, 7000 Mons, Belgium
Interests: heterocycles; medicinal chemistry; green chemistry; microwave-induced synthesis
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

The last century has clearly demonstrated the impact of technology on society. As the industrial processing continues the drive towards higher performance and lower costs, demanding new synthesis processes become a necessity. Balanced with the performance and quality requirements for current and future processing materials are the Environmental, Safety and Health concerns surrounding these processes. The shape and direction of further technological development also has to consider that many of these process steps are critically dependent on energy transfer into the reaction to deliver the highest levels of process performance and end-product reliability.

Microwave (MW) heating is a technique of heating dielectric materials, i.e., materials that have no or low electrical conductivity; in most cases these materials are also poorly conductive thermally. Conventional heating techniques, based on heat transfer phenomena, are inefficient for heating dielectrics. MW techniques dissipate heat within the material by an electromagnetic phenomenon of energy transfer. When discussing the performance of the microwave technique in comparison with other dielectric heating techniques (i.e., radio frequency), there are two main advantages that should be highlighted: high energy transfer due to higher frequency (915 MHz or 2450 MHz vs. 13.56 MHz or 27.12 MHz) and reduced breakdown risk due to the lower electric field strength.

It is well known that energy is often one of the most significant uncontrolled variables in an experiment. Microwaves have the potential to change that, partly by the fundamental way the energy is delivered to the molecules of interest, and partly by the electronic controls in the apparatus, facilitating the setting and recording of time, energy level, final temperature and so forth.

The present Special Issue of Molecules entitled “Microwave-Assisted Organic Synthesis” aims to attract all scientists working in the synthesis and characterization of microwave-assisted synthesis without restrictions to the value of the microwave frequency, the phase of the system, and the scale of the performed process. All papers submitted are welcome as we hope this effort to bring the SMM community together will receive the appreciation and support it deserves.

Dr. Marilena Radoiu
Dr. Jean Jacques Vanden Eynde
Dr. Annie Mayence
Guest Editors

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Molecules is an international peer-reviewed open access semimonthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2700 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.


Keywords

  • microwaves assisted chemistry
  • plasma
  • frequency
  • catalysis

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Published Papers (5 papers)

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Research

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2519 KiB  
Communication
Microwave-Assisted Superheating and/or Microwave-Specific Superboiling (Nucleation-Limited Boiling) of Liquids Occurs under Certain Conditions but is Mitigated by Stirring
by Anthony Ferrari, Jacob Hunt, Albert Stiegman and Gregory B. Dudley
Molecules 2015, 20(12), 21672-21680; https://doi.org/10.3390/molecules201219793 - 4 Dec 2015
Cited by 22 | Viewed by 6497
Abstract
Temporary superheating and sustained nucleation-limited “superboiling” of unstirred liquids above the normal atmospheric boiling point have been documented during microwave heating. These phenomena are reliably observed under prescribed conditions, although the duration (of superheating) and magnitude (of superheating and superboiling) vary according to [...] Read more.
Temporary superheating and sustained nucleation-limited “superboiling” of unstirred liquids above the normal atmospheric boiling point have been documented during microwave heating. These phenomena are reliably observed under prescribed conditions, although the duration (of superheating) and magnitude (of superheating and superboiling) vary according to system parameters such as volume of the liquid and the size and shape of the vessel. Both phenomena are mitigated by rapid stirring with an appropriate stir bar and/or with the addition of boiling chips, which provide nucleation sites to support the phase-change from liquid to gas. With proper experimental design and especially proper stirring, the measured temperature of typical organic reaction mixtures heated at reflux will be close to the normal boiling point temperature of the solvent, whether heated using microwave radiation or conventional convective heat transfer. These observations are important to take into consideration when comparing reaction rates under conventional and microwave heating. Full article
(This article belongs to the Special Issue Microwave-Assisted Organic Synthesis)
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3156 KiB  
Article
Molecular Differentiated Initiator Reactivity in the Synthesis of Poly(caprolactone)-Based Hydrophobic Homopolymer and Amphiphilic Core Corona Star Polymers
by Eileen Deng, Nam T. Nguyen, Frédéric Hild, Ian E. Hamilton, Georgios Dimitrakis, Samuel W. Kingman, Phei-Li Lau and Derek J. Irvine
Molecules 2015, 20(11), 20131-20145; https://doi.org/10.3390/molecules201119681 - 9 Nov 2015
Cited by 6 | Viewed by 7697
Abstract
Macromolecules that possess three-dimensional, branched molecular structures are of great interest because they exhibit significantly differentiated application performance compared to conventional linear (straight chain) polymers. This paper reports the synthesis of 3- and 4-arm star branched polymers via ring opening polymerisation (ROP) utilising [...] Read more.
Macromolecules that possess three-dimensional, branched molecular structures are of great interest because they exhibit significantly differentiated application performance compared to conventional linear (straight chain) polymers. This paper reports the synthesis of 3- and 4-arm star branched polymers via ring opening polymerisation (ROP) utilising multi-functional hydroxyl initiators and Sn(Oct)2 as precatalyst. The structures produced include mono-functional hydrophobic and multi-functional amphiphilic core corona stars. The characteristics of the synthetic process were shown to be principally dependent upon the physical/dielectric properties of the initiators used. ROP’s using initiators that were more available to become directly involved with the Sn(Oct)2 in the “in-situ” formation of the true catalytic species were observed to require shorter reaction times. Use of microwave heating (MWH) in homopolymer star synthesis reduced reaction times compared to conventional heating (CH) equivalents, this was attributed to an increased rate of “in-situ” catalyst formation. However, in amphiphilic core corona star formation, the MWH polymerisations exhibited slower propagation rates than CH equivalents. This was attributed to macro-structuring within the reaction medium, which reduced the potential for reaction. It was concluded that CH experiments were less affected by this macro-structuring because it was disrupted by the thermal currents/gradients caused by the conductive/convective heating mechanisms. These gradients are much reduced/absent with MWH because it selectively heats specific species simultaneously throughout the entire volume of the reaction medium. These partitioning problems were overcome by introducing additional quantities of the species that had been determined to selectively heat. Full article
(This article belongs to the Special Issue Microwave-Assisted Organic Synthesis)
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847 KiB  
Article
Synthetic Development of New 3-(4-Arylmethylamino)butyl-5-arylidene-rhodanines under Microwave Irradiation and Their Effects on Tumor Cell Lines and against Protein Kinases
by Camille Déliko Dago, Christelle N´ta Ambeu, Wacothon-Karime Coulibaly, Yves-Alain Békro, Janat Mamyrbékova, Audrey Defontaine, Blandine Baratte, Stéphane Bach, Sandrine Ruchaud, Rémy Le Guével, Myriam Ravache, Anne Corlu and Jean-Pierre Bazureau
Molecules 2015, 20(7), 12412-12435; https://doi.org/10.3390/molecules200712412 - 8 Jul 2015
Cited by 12 | Viewed by 6800
Abstract
A new route to 3-(4-arylmethylamino)butyl-5-arylidene-2-thioxo-1,3-thiazolidine-4-one 9 was developed in six steps from commercial 1,4-diaminobutane 1 as starting material. The key step of this multi-step synthesis involved a solution phase “one-pot two-steps” approach assisted by microwave dielectric from N-(arylmethyl)butane-1,4-diamine hydrochloride 6af [...] Read more.
A new route to 3-(4-arylmethylamino)butyl-5-arylidene-2-thioxo-1,3-thiazolidine-4-one 9 was developed in six steps from commercial 1,4-diaminobutane 1 as starting material. The key step of this multi-step synthesis involved a solution phase “one-pot two-steps” approach assisted by microwave dielectric from N-(arylmethyl)butane-1,4-diamine hydrochloride 6af (as source of the first point diversity) and commercial bis-(carboxymethyl)-trithiocarbonate reagent 7 for construction of the rhodanine platform. This platform was immediately functionalized by Knoevenagel condensation under microwave irradiation with a series of aromatic aldehydes 3 as second point of diversity. These new compounds were prepared in moderate to good yields and the fourteen synthetic products 9an have been obtained with a Z-geometry about their exocyclic double bond. These new 5-arylidene rhodanines derivatives 9an were tested for their kinase inhibitory potencies against four protein kinases: Human cyclin-dependent kinase 5-p25, HsCDK5-p25; porcine Glycogen Synthase Kinase-3, GSK-3α/β; porcine Casein Kinase 1, SsCK1 and human HsHaspin. They have also been evaluated for their in vitro inhibition of cell proliferation (HuH7 D12, Caco 2, MDA-MB 231, HCT 116, PC3, NCI-H727, HaCat and fibroblasts). Among of all these compounds, 9j presented selective micromolar inhibition activity on SsCK1 and 9i exhibited antitumor activities in the HuH7 D12, MDA-MBD231 cell lines. Full article
(This article belongs to the Special Issue Microwave-Assisted Organic Synthesis)
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794 KiB  
Article
Microwave-Assisted Condensation Reactions of Acetophenone Derivatives and Activated Methylene Compounds with Aldehydes Catalyzed by Boric Acid under Solvent-Free Conditions
by Elodie Brun, Abdelmounaim Safer, François Carreaux, Khadidja Bourahla, Jean-Martial L'helgoua'ch, Jean-Pierre Bazureau and Jose Manuel Villalgordo
Molecules 2015, 20(6), 11617-11631; https://doi.org/10.3390/molecules200611617 - 23 Jun 2015
Cited by 19 | Viewed by 8189
Abstract
We here disclosed a new protocol for the condensation of acetophenone derivatives and active methylene compounds with aldehydes in the presence of boric acid under microwave conditions. Implementation of the reaction is simple, healthy and environmentally friendly owing to the use of a [...] Read more.
We here disclosed a new protocol for the condensation of acetophenone derivatives and active methylene compounds with aldehydes in the presence of boric acid under microwave conditions. Implementation of the reaction is simple, healthy and environmentally friendly owing to the use of a non-toxic catalyst coupled to a solvent-free procedure. A large variety of known or novel compounds have thus been prepared, including with substrates bearing acid or base-sensitive functional groups. Full article
(This article belongs to the Special Issue Microwave-Assisted Organic Synthesis)
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Review

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2391 KiB  
Review
Heterogeneous Phase Microwave-Assisted Reactions under CO2 or CO Pressure
by Emanuela Calcio Gaudino, Laura Rinaldi, Laura Rotolo, Diego Carnaroglio, Camillo Pirola and Giancarlo Cravotto
Molecules 2016, 21(3), 253; https://doi.org/10.3390/molecules21030253 - 24 Feb 2016
Cited by 8 | Viewed by 5850
Abstract
The present review deals with the recent achievements and impressive potential applications of microwave (MW) heating to promote heterogeneous reactions under gas pressure. The high versatility of the latest generation of professional reactors combines extreme reaction conditions with safer and more efficient protocols. [...] Read more.
The present review deals with the recent achievements and impressive potential applications of microwave (MW) heating to promote heterogeneous reactions under gas pressure. The high versatility of the latest generation of professional reactors combines extreme reaction conditions with safer and more efficient protocols. The double aims of this survey are to provide a panoramic snapshot of MW-assisted organic reactions with gaseous reagents, in particular CO and CO2, and outline future applications. Stubborn and time-consuming carbonylation-like heterogeneous reactions, which have not yet been studied under dielectric heating, may well find an outstanding ally in the present protocol. Full article
(This article belongs to the Special Issue Microwave-Assisted Organic Synthesis)
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