Action Of Microwave Irradiation Research Articles

One-step transformation of the marine alkaloid fascaplysin into homofascaplysins B and B-1. The first syntheses of 3-bromohomofascaplysin B and 3–bromohomofascaplysin B-1

A method for one-step conversion of the marine alkaloid fascaplysin into homofascaplysins B and B-1 was elaborated. It was also used for the first syntheses of the marine alkaloids 3–bromohomofascaplysin B and 3-bromohomofascaplysin B-1. The best results were demonstrated under the action of microwave irradiation in presents of dihydroquinone as a reducing agent.

Facile Microwave‐assisted Synthesis of 1,3,5‐Trisubstituted Pyrazoline Derivatives Incorporating Sulfonyl Moiety

AbstractWe developed an environmentally benign, convenient microwave‐assisted process for the construction of 1,3,5‐trisubstitued pyrazolines (10a∼10f, 11a∼11f, 12a∼12f, 13a∼13f). Chalcones, as the key intermedi‐ ates, were obtained by the condensation of each of appropriately substituted aromatic aldehydes (1∼4) with 4‐substituted acetophenones (5a∼5f) via a Claisen‐Schmidt reaction under the action of microwave irradiation. Cyclization of the chalcones (6a∼6f, 7a∼7f, 8a∼8f, 9a∼9f) with p‐toluene sulfonhydrazide af‐ forded 1,3,5‐trisubstitued pyrazoline derivatives using microwave‐assisted process in 25 min and 140 watt power in glycol. The structures of targeted compounds were established by IR, 1H NMR, MS and ele‐ mental analysis. The results indicate that microwave‐assisted synthetic process presents advantages in terms of enhancement in rate, decrease in reaction time, clean reaction and convenient operation.

Simple and efficient microwave-assisted polycondensation for preparation of chiral poly(amide-imide)s having pendant phenol moiety

Chiral bisaminoacids were synthesized by interaction of pyromellitic dianhydride with different aminoacids (phenylalanine, leucine, isoleucine, valline and alanine) in boiling glacial AcOH. Polycondensation of prepared bisaminoacids with aromatic diamine, containing pendant hydroxyl-groups, was carried out in molten tetrabutylammonium bromide under action of microwave irradiation. With yields 88–96% were prepared optically active polyamidoimides (PAIs), having inherent viscosities from 0.30 to 0.58 dL/g (0.5% solution in DMF, 25°C) and [α]58925= −28...−48 deg. As shown X-ray diffraction and emission scanning electron microscopy, PAIs are nanostructured and amorphous polymers.

Formation of Bimetallic Au–Pd and Au–Pt Nanoparticles under Hydrothermal Conditions and Microwave Irradiation

The reduction of chlorocomplexes of gold(III) from muriatic solutions by nanocrystal powders of palladium and platinum at 110 and 130 °C under hydrothermal conditions and the action of microwave irradiation has been investigated. The structure and composition of the solid phase have been characterized by transmission electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, and chemical methods. Bimetallic particles with a core-shell structure have been revealed. The obtained particles are established to have a core of the metal reductant covered with a substitutional solid (Au, Pd) solution in case of palladium, and isolated by a gold layer in the case of platinum. The main reason for such a difference is the ratio between the rates of aggregation and reduction. It has been shown by the example of the Au-Pd system that the use of microwave irradiation allows us not only to accelerate the synthesis of particles but also to obtain more homogeneous materials in comparison with conventional heating.

Interaction of 3-acetoacetyl-2H-chromen-2-one with azanucleophilic reagents

The reactions of 3-acetoacetylchromen-2-one with mono- and binucleophilic reagents, under the action of microwave irradiation have been studied. It was shown that depending on the nucleophilicity of the reactant new heterocyclic systems were formed involving the oxo group of the substituent in position 3 of the heterofragment, its opening, or recyclization.

Preconcentration of noble metals with the POLYORGS 4 complexing sorbent under the action of microwave irradiation

The sorption of Au(III), Pd(II), Pt(IV), Rh(III), and Ir(IV) with the POLYORGS 4 complexing sorbent in the static mode was studied at room temperature and on thermal and microwave heating. It was demonstrated that the sorption of noble metals from 1 M HCl and 1 M HNO3 solutions can be substantially accelerated under the action of microwave irradiation. Based on the obtained data, the conditions of the group preconcentration of noble metals for their subsequent determination by the ETAAS and ICP AES methods were selected. The preconcentration procedure was used for the analysis of certified reference material SARM-7B (platinum-containing ore), VT-1 (copper-nickel sulfide ore), and the alloy of copper with noble metals.

Determination of Aniline in Water by Microwave-Assisted Headspace Solid-Phase Microextraction and Gas Chromatography

Determination of aniline in wastewater was investigated by microwave-assisted headspace solid-phase microextraction (MA-HS-SPME), for one-step in-situ sample preparation, and gas chromatography. Aniline in the water was evaporated into the headspace under the action of microwave irradiation and adsorbed directly by the SPME fiber. After desorption in the GC injection port and gas chromatography aniline was detected by FID. Conditions affecting the extraction efficiency, for example the pH of the water, addition of salt, microwave power and irradiation time, and desorption conditions were investigated. Experimental results indicated that adjustment of the pH of the water sample to 12 and headspace SPME sampling with a PDMS-DVB fiber under medium–high power irradiation (345 W) for 3 min resulted in the best extraction efficiency. Desorption of aniline was optimum when the SPME fiber was heated at 230 °C for 3 min. The detection limit was approximately 0.01 μg mL−1. The proposed method is a simple, fast, and organic-solvent-free procedure for analysis of aniline in water. Application was illustrated by analysis of aniline in wastewater from a polymer factory.

Synthesis of beta-lactams from diazoketones and imines: the use of microwave irradiation.

[see reaction]. The transformation of diazoketones derived from alpha-amino acids to ketenes that, in turn, react further with imines to afford beta-lactams, can be realized not only by utilizing photochemical reaction conditions but also under the action of microwave irradiation. Under the latter reaction conditions 4-alkenyl-substituted beta-lactams derived from amino acids, substrates that were not previously accessible, have been prepared. beta-Lactams possessing a trans-substitution pattern at the ring were obtained exclusively.

Deproteinization of blood serum by acid treatment and microwave irradiation for the determinationof aluminium by electrothermal atomicabsorption spectrometry

A method of deproteinizing serum was employed to reduce the protein concentration in the determination of aluminium by electrothermal atomic absorption spectrometry. The procedure combines the action of microwave irradiation with acids, at a concentration 10 times lower than that in the usual acid deproteinization methods, and promotes a protein reduction >99% with a small dilution factor (1+1). The best results with respect to aluminium determination were obtained with trichloroacetic acid at a concentration of 1.0%. Before the deproteinization procedure for recovery measurements, serum samples were submitted to an incubation treatment at 37 °C to bond aluminium ions to the proteins. The proposed method was compared with the usual deproteinization with acids for the separation of proteins, and for the determination of aluminium with direct injection of diluted serum samples into the graphite furnace. The regression for the correlation analysis of the proposed method and the direct determination of aluminium, applied to the analysis of 20 serum samples, indicated that the deproteinization procedure is efficient and generates comparable results. The reduction of the proteins allowed the use of a simple and fast graphite furnace heating programme for the analysis of serum samples without matrix interferences.

Combined action of microwave irradiation and local cooling on living tissues

Combined action of microwave irradiation and local cooling on living tissues