Current Microwave Chemistry (v.3, #2)

Meet Our Editorial Board Member by Qi-Huang Zheng (91-91).

First Bioreduction of 2,2,2-trifluoro-1-phenylethanone by Whole Hyphae of Marine Fungus Mucor racemosus CBMAI 847 Under Microwave Radiation by Sandra Santos Ribeiroa, Lara Durães Sette, André Luiz Meleiro Porto Meleiro Porto (92-96).
This paper reports on the asymmetric reduction of 2,2,2-trifluoro-1-phenylethanone 1a to the corresponding (S)-2,2,2-trifluoro-1-phenylethanol 1b by marine fungus M. racemosus CBMAI 847 under conventional heating (CH) and microwave radiation (MW). The results show that (S)-alcohol was obtained with good conversion (64-100%) and enantiomeric excess (74-99%) for both methods performed under conventional heating (orbital shaking) and microwave radiation. When 2,2,2- trifluoro-1-phenylethanone 1a was reduced by fungus under microwave radiation, the methodology showed to be very efficient to obtain enantiomerically pure alcohol 1b in comparison to the conventional heating. This is the first report on the use of microwave-assistant in biocatalytic reactions catalyzed by marine fungus.

Microwave Assisted Reactions of 5-Amino-1, 3-disubstituted Pyrazoles with Some Benzaldehydes by Agnieszka Puchala, Magdalena Marcinkowska, Danuta Rasala (97-101).
The microwave-promoted reactions of 5-amino-1,3-disubstituted pyrazoles with benzaldehyde, 4-chloro- and 4-nitrobenzaldehydes are presented. The use of microwave irradiation with variable input power leads to different products, such as Schiff bases, diamine derivatives and bispyrazolo[ 3,4-b;4'3'-e]pyridines in moderate to excellent yields and high purities.

Influence of Microwave-Assisted Synthesis Parameters on ZSM-11 Zeolite Production Without Seeding by Federico Azzolina-Jury, Frédéric Thibault-Starzyk (102-113).
A novel and complete study of microwave-assisted synthesis parameters for ZSM-11 zeolite is provided. Several parameters were studied such as aging time, synthesis temperature, silica source, Si/Al molar ratio, template agent concentration and residence time of the initial synthesis mixture under microwave irradiation and conventional heating. Novel framework zeolite shifts from MEL to MFI, as well as the Ostwald ripening mechanism were observed. The microwave-assisted synthesis of ZSM-11without seeding was optimized after a complete study of the synthesis parameters.

Comparative Kinetic Study on the Preparation of Poly(Vinyl Acetate) Activated by Microwave and Conventional Heating by Jessica Olvera-Mancilla, Larissa Alexandrova, Vladimir Alonso Escobar-Barrios, Joaquín Palacios-Alquisira (114-123).
Background: Microwaves (MW) activation often leads to higher yields and more selective products are obtained, compared to the same reaction activated by conventional heating (CH). In polymer science, the use of MW irradiation has been widely investigated; nevertheless few articles are dedicated to controlled radical polymerization reaction (CRP). Considering the relative difficulty of vinyl acetate (VAc) polymerization, we decided to concentrate our attention on the kinetic aspect of the process. In this work MW versus CH activation reactions are discussed. Solvent effects in the presence of RuII complexes were considered and MW power effect studied.
Methods: In this work, we report the effect of solvent media on the polymerization reaction of VAc monomer, under controlled conditions of temperature and molar ratio [VAc]0/[RuII]0/[Al]0/[CCl4]0 = 200/1/1/1. The reactions were activated by MW and CH. The conversion vs. time and molecular weight vs. time are important characteristics of this system. Four different solvents were tested with low and high dielectric constants DMSO, DMF, anisole, MEK; three RuII complexes were probed mediating the polymerization reaction.
Results: In experiments with MW activation, the effect of solvent media was clear, since the DMSO solvent with the highest value of dielectric constant (), produced the best yield and molecular weight (Mn, GPC), under controlled temperature of 70°C and power conditions, 100, 500 W. For reactions activated by CH, the solvent effect was important too; values of % conversion and Mn, GPC in DMSO did follow a clear trend; good molecular weight values and high conversion were observed. There is a clear and interesting difference in the reaction time between both methods of activation, CH and MW. For the same % conversions, the reaction time is ten times shorter when activated by MW, the conversion with MW reaches 42% in 45 min, and 46% conversion in 600 min was observed with CH. RuII- 1 complex was effective for the preparation of polymers under MW in DMSO. This complex is cationic and presents an activated structure more quickly under MW than CH. It was found that polymerization reaction rate decreases in the following order MW > CH.
Conclusion: The kinetic data were analyzed using a first-order model. The reaction kinetics are very much dependent on the activation method, as an example kp, MW = 1x10-2 y kp, CH = 6x10-4, so, these values indicate that the reaction activated by MW proceeds 16.4 times faster than the reaction activated by CH. The character of the VAc polymerization reaction under MW, in the presence of DMSO as a solvent, goes on by a living polymerization mechanism, the molecular weight increases with conversion and it is very similar in value to the theoretical molecular weight. The living character was probed and confirmed through the formation of the copolymer p(VAc-co-MMA).

A Facile, Microwave-Assisted Synthesis of an Adenosine-Ribose Probe for Binding-Based Profiling of Nucleoside and Nucleotide-Binding Proteins by Matthew R. Battistini, Shikha Mahajan, Daili Diaz, Lindsey N. Shaw, David J. Merkler (124-130).
Herein, we describe a novel, microwave-assisted synthesis of a binding-based probe capable of enriching proteins that bind adenine ribose derivatives (AdoRs). We employed this probe in activity- based protein profiling studies to qualitatively assess the AdoR-binding proteome in three bacterial cell lines from the genus Bacillus. This proof of concept experiment demonstrated a unique subset of proteins distinctive to each species, and confirmed the efficacy of the probe tagging and subsequent enrichment.

Hydrogenation of pyridine under Microwave (MW) dielectric heating is a valuable method for a rapid approach to piperidine synthesis. Starting from easily available pyridinecarboxylate derivatives, aminopipecolic scaffolds were prepared and further decorated with a procedure potentially useful for parallel synthesis. MW hydrogenation on PtO2 proceeded with high stereoselectivity and low catalyst loading under mild conditions (80°C and 850 MPa of H2 pressure). MWs were also effective to perform a Pinner reaction on 2-cyano-nitropyridines to obtain the corresponding methyl nitropyridine carboxylates. A general procedure to decorate the 3-, 4-, and 5-amino-pipecolic derivatives obtained from the pyridine hydrogenation has been also developed.

The Electrical Property of Large Few Layer Graphene Flakes Obtained by Microwaves Assisted Exfoliation of Expanded Graphite by Azhar A. Pirzado, Guillaume Dalmas, Lam Nguyen-Dinh, Ivan Komissarov, Francois Le Normand, Izabela Janowska (139-144).
Few layer graphene (FLG) was synthesized by -wave assisted exfoliation of expanded graphite in toluene with an overall yield from c.a. 7% to 20%. A significant difference in the absorption of -waves by the expanded graphite and toluene allowed a rapid heating of the medium. The number of FLG sheets varies from 3 to 12, while the lateral size of the sheets exceeds few ms. The obtained FLG exhibits very low resistance with average value of 1.6 k (500 minimum) which is comparable to that of high quality graphenes synthesized by CVD methods, and lower than numbers of exfoliated graphenes.

Microwave Assisted Prospective Synthesis of New 5-Arylidene Rhodanine Derivatives Bearing a 3-[4-(3-Aminopropyl)piperazin-1-yl]propyl Side Chain by Christelle N';ta Ambeu, Camille Déliko Dago, Wacothon Karime Coulibaly, Yves-Alain Békro, Janat A. Mamyrbékova-Békro, Jean Pierre Bazureau (145-156).
A series of (5Z) 5-arylidene 2-thioxo-1,3-thiazolidin-4-one derivatives 7(a-l) bearing a [4-(3-aminopropyl)piperazin-1-yl]propyl side chain in N-3 position was prepared using a solution phase protocol assisted by microwave dielectric heating. These new compounds were synthesized in four steps with overall yields ranging from 12 to 33% via a "one-pot two-steps" protocol based on Holmberg reaction followed by a stereocontrolled Knoevenagel condensation. The rhodanine intermediate 4' issued from Holmberg reaction under microwave was also isolated and identified by spectroscopic methods of analysis. The twelve deprotected products 7(a-l) have been obtained with a Z-geometry about their exocyclic double bond. All N-Boc intermediates 6(a-l) and deprotected rhodanine derivatives 7(a-l) issued from trifluoroacetic acid treatment have been characterized by 1H, 13C and HRMS.

Background: Novel ways of increasing the performance of heterogeneous catalysis are always being sought. Microwave irradiation is one such potential pretreatment method and is expected to be useful in the modification (for better or worse) of iron-based catalysts since the iron oxide precursors are good microwave radiation absorbers.
Methods: Iron based Fischer-Tropsch catalysts were subjected to microwave radiation and their catalytic performance compared with untreated samples. Surface and bulk characterization were carried out in order to try to explain any changes in catalytic behavior observed.
Results: Increases in activity and changes in selectivity (methane, olefins, growth probability, water gas shift contribution) have both been observed and the mode of interaction appears to involve potassium mobilization when added as a promotor, since potassium: silica and potassium: iron surface elemental abundances are changed by the radiative treatment. The surface properties of the catalysts are modified, as detected by the temperature programmed surface reaction (TPSR) of adsorbed carbon monoxide with hydrogen. The TPSR profiles seen are sensitive to both the duration and power level of microwave radiation used.
Conclusion: Microwave radiation can be used to modify the behavior of iron-based catalysts and appears to work by causing changes in the surface rather hen the bulk properties of the solids. Elemental abundances at the surface change as does the chemisorption of carbon monoxide and reactivity of the latter with hydrogen. The effects are easily induced and appear to be long-lived.

Rapid and Convenient CuCl2 Catalysed Microwave-Assisted Synthesis of Novel Spiro [indoline-3,4'-quinoline] Derivatives by Mayuri A. Borad, Manoj N. Bhoi, Darshita M. Patel, Hitesh D. Patel (166-172).
A rapid and efficient, one-pot, three-component, microwave-assisted synthesis of spiro[indoline-3,4'-quinoline] derivatives has been accomplished through three-component Knoevenagel/ Michael addition reaction of isatin, malononitrile and various amine derivative in very good to outstanding yields under CuCl2 catalyst. The main benefits of this protocol are simple work-up, trivial and eco-friendly reaction conditions. Biological characterization, including antibacterial was also evaluated.

Background: To carry out the hydrolysis of a bromomethylthiophenone to a hydroxymethylthiophenone, expensive silver triflate has to be used. We wanted to decrease the cost of this step.
Methods: Microwave heating in dimethyl sulfoxide and water was used to perform the above mentioned hydrolysis.
Results: The hydrolysis could be done in a scale up to one gram and the isolated yields were from 51 to 62%.
Conclusion: The best conditions for the hydrolysis were microwave irradiation in water and dimethyl sulfoxide at 100°C. Although the yields in the reaction were moderate and only around 70% of the starting material was accounted for, are the reaction conditions very simple and the reagents very cost effective.