Microwave-induced Synthesis Research Articles

Microwave-Induced Synthesis of Some Novel Fungicidal Pyrazole Derivatives

A series of novel pyrazole derivatives have been synthesized from propanoyl hydrazine and aromatic aldehydes under microwave irradiations. The reaction leads to condensation in ethanolic solution to give corresponding hydrazones which undergo subsequent cyclisation to furnish pyrazole derivatives in presence of formic acid. The reaction rate is enhanced considerably by using microwaves with excellent yield as compared to conventional heating method. The reactions took 4-7 minutes for completion with 78-92% yield. All the synthesized pyrazole derivatives showed promising antifungal activities against Aspergillus niger and Aspergillus Flavus. Microwave-induced organic synthesis has been proved quite beneficial and eco-friendly method in terms of limited use of chemicals, short reaction time and good yield with higher degree of purity.DOI: http://dx.doi.org/10.3126/jncs.v30i0.9385Journal of Nepal Chemical Society Vol. 30, 2012 Page: 138-142 Uploaded date: 12/20/2013

Microwave-induced synthesis of β-cyclodextrin/N-doped carbon nanotube polyurethane nanocomposites for water purification

The fabrication of polymer nanocomposites for the removal of organic species in aqueous media is achieved using conventional methods. However, these methods are expensive and deteriorating to the environment due to high energy demands and high organic solvent volume requirements. This work discusses the synthesis of nanocomposite polymers of β-cyclodextrin (β-CD) and nitrogen-doped carbon nanotubes (N-CNTs) under microwave irradiation for the first time. This novel method is efficient, greener and time saving. Typically, the reaction to prepare β-CD polymers takes about 24h. Here we report a novel method to synthesize the polymers in 10min. N-CNTs were synthesized via chemical vapour deposition method (CVD) using a 10wt% Fe–Co/CaCO3 catalyst. The N-CNTs were found to contain ∼2at% nitrogen by CN analysis. The N-CNTs were of high purity and were oxidized with acid functional groups (–COOH, –CO, –OH) using nitric acid under reflux. Zeta potential studies indicated that the quantity of acid functional groups increases with increase in acid treatment times. The functionalised N-CNTs (fN-CNTs) were then polymerized with β-CD using hexamethylene diisocyanate as the functional cross-linker in a microwave under an inert gas atmosphere. The polymers showed an efficient removal of p-nitrophenol from spiked water samples as confirmed by UV–Vis spectroscopy.

Rapid Microwave-Induced Synthesis of Gold-Polydimethylsiloxane Nanocomposites for Biosensing of Proteins

In this paper a novel in-situ microwave-induced synthesis of the gold-polydimethylsiloxane nanocomposite is presented. Microwave-induced synthesis has the advantages of a very short reaction time, small particle size and narrow size distribution of the particles. The ethanol solution of gold chloroauric acid is used as the precursor solution. The mechanism of formation and growth of nanoparticles are discussed in detail. UV/Vis spectroscopy and SEM imaging were used to characterize the optical properties and the size distribution of the particles. To improve the sensing properties of the nanocomposite, an annealing process were used. The results show that the annealed samples have the high sensitivity of 102 nm/RIU toward the surrounding medium which makes the nanocomposite suitable for biosensing applications. In addition, the elasticity of the platform in the presence of gold nanoparticles was found to be enhanced up to 20%. Finally, the immunosensing of the bovine growth hormone was performed by using the localized surface plasmon resonance (LSPR) band of gold nanoparticles. The results demonstrate suitability of the nanocomposite platform for biosensing applications. The results are highly relevant for microfluidic-based biosensors.

Microwave-Induced Solvent-Free Synthesis and Antifungal Screening of Novel Spiro Heterocyclic Systems Containing 3,5-Diphenyl-7H-thiazolo[3,2-a]pyrimidine and Indolin-2-one

A microwave-induced technique has been developed for the synthesis of a series of novel spiro indoline-based heterocycles (7a–g) at atmospheric pressure in an open vessel using an environmentally benign procedure. This rapid method produces pure products in good yields within a few minutes in comparison to the conventional procedure developed for the synthesis of these heterocycles. The synthesized compounds have been screened in vitro for antifungal activity against two fungal strains (i.e., Aspergillus niger and Aspergillus flavus). All compounds have shown significant activity against these pathogens. [Supplementary materials are available for this article. Go to the publisher's online edition of Synthetic Communications® for the following free supplemental resource: Full experimental and spectral details.]

Microwave-induced synthesis of alginate–graft-poly(N-isopropylacrylamide) and drug release properties of dual pH- and temperature-responsive beads

The first decade of the 21st century saw an increasing interest in the development of devices and biomaterials for delivery of bioactive substances that can be controlled by external stimuli. This study deals with the production of novel pH and temperature responsive beads for colon-specific delivery of indomethacine (IM). For this purpose, N-isopropylacrylamide (NIPAAm) was grafted onto sodium alginate (NaAlg) with microwave radiation in aqueous solution. The graft copolymer (NaAlg-g-PNIPAAm) was characterized by using attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR), elemental analysis, differential scanning calorimetry (DSC), and thermogravimetric analysis. A series of pH- and temperature-responsive NaAlg-g-PNIPAAm beads were prepared as drug delivery matrices of indomethacine cross-linked by glutaraldehyde (GA) in the hydrochloric acid catalyst. Preparation condition of the beads was optimized by considering the percentage entrapment efficiency, particle size, swelling capacity of beads, and their release data. Effects of variables such as graft yield, drug/polymer ratio, exposure time to GA, and concentration of GA on the release of IM were investigated and discussed at two different pH values (1.2 and 7.4) and temperatures (25°C and 37°C). It was observed that IM release from the beads decreased when the grafting of NIPAAm, drug/polymer ratio (d/p), and extent of cross-linking were increased. The results also showed that NaAlg-g-PIPAAm beads were positive pH and temperature responsive. The release of IM from grafted beads was slower for the pH 1.2 solution than that of the pH 7.4 buffer solution, whereas the release rate was higher at 37°C than at 25°C.

A facile microwave-induced synthesis of titanium pyrophosphate nanocrystals

Titanium pyrophosphate (TiP2O7) nanocrystals are synthesized using a facile microwave (MW) heating method, in which titanium hydroxide (TH) and H3PO4 (85%) are used as Ti and P sources without surfactant or template assistance. X-ray diffraction results suggest that pure cubic-structured TiP2O7 could be obtained via MW irradiation at 800W for 5min. Scanning electron microscope and transmission electron microscope photographs show that the grain sizes of the samples range from 20nm to 100nm and vary with the irradiation time. The effects of different sample preparation conditions on the experimental result are also discussed. The band gap energy of as-synthesized TiP2O7 is determined to be 3.8eV by UV diffuse reflectance spectral analysis. Luminescence spectral analysis shows that nanocrystal TiP2O7 shows white-light emission at 300nm.

A highly efficient, simple, and ecofriendly microwave-induced synthesis of indolyl chalcones and pyrazolines

One-pot synthesis of indolyl chalcones (3a–c) employing indole-3-carboxaldehyde (1) and heteroaryl active methyl compounds (2a–c) under microwave irradiation is described. The indolyl chalcones (3a–c) are transformed into medicinally important pyrazolines (5a–f) using different hydrazines. Application of microwave irradiation leads to many remarkable advantages, such as solvent- and catalyst-free reaction conditions, simple work up procedure, shorter reaction time, in addition to ecofriendly ‘green chemistry’ economical and environmental impacts.

Luminescence of nano- and macrosized LaPO 4:Ce,Tb excited by synchrotron radiation

Comparing the luminescence properties of nanosized and macroscopic LaPO 4:Ce,Tb powders are performed in wide spectral range using synchrotron radiation. In the present study, LaPO 4:Ce,Tb nanopowder was produced by means of a microwave-induced synthesis in ionic liquids, whereas the bulk sample represents a commercial lamp phosphor. Emission and excitation of both, Ce 3+ and Tb 3+ luminescence, is observed to be different when comparing bulk and nanosized LaPO 4:Ce,Tb. In particular, it was shown that the fine structure of the Ce 3+ as well as the Tb 3+ related emission is poorly resolved for the nanomaterial. It is suggested that the nanoparticles surface plays a key role regarding the perturbation of rare-earth ions and changes their luminescence properties. Furthermore, it is demonstrated that allowed f–d transitions on Tb 3+ at high energy are significantly suppressed for nanosized LaPO 4:Ce,Tb. Energy transfer is required to initiate Tb 3+ emission even in the vacuum ultraviolet spectral range.

Microwave-Induced Synthesis of Carboxymethyl Hemicelluloses and Their Rheological Properties

In this article, a facile, rapid, and efficient method was developed for the preparation of carboxymethyl hemicelluloses using microwave-induced organic reaction enhancement chemistry. The influences of the factors including reaction time, temperature, and the amount of sodium monochloroacetate and sodium hydroxide on the degree of substitution (DS) of the products were investigated. The rheological properties and the chemical structure of the resulting polymers were also studied. It was found that microwave irradiation could significantly promote the chemical reaction efficiency and accelerate the carboxymethylation of hemicelluloses with sodium monochloroacetate. Therefore, carboxymethyl hemicelluloses with higher DS of 1.02 could be obtained in much shorter time scales as compared to the conventional heating method. Results from rheological analysis indicated that carboxymethyl hemicellulose solutions exhibited shear-thinning behavior in the range of shear rates tested and showed lower viscosity and modulus in comparison with those of the native hemicelluloses due to lower molecular weight and the role of carboxymethyl groups in reducing the entanglements between hemicelluloses chains.

Microwave-Induced Synthesis and Bioactivity of [3-Phenoxy-methyl-4-phenyl-1,2,4-triazole-5-yl-thio]acetyl Hydrazone Derivatives

A convenient method for the preparation of hydrazone derivatives from condensation reaction of [3-phenoxymethyl-4-phenyl-1,2,4-triazole-5-yl-thio]acetyl hydrazine with various substituted benzaldehydes under conditions of microwave irradiation has been developed. This method has many merits including high yields, short reaction times, ease of work-up, and simple operation. All of the compounds have been characterized by 1H NMR, 13C NMR, IR spectra and elemental analysis. In addition, the preliminary biological activity tests showed that some of the title compounds remarkably enhanced the root elongation of rape seedings; moreover, some compounds possessed antibacterial activity against Bacillus subtilis. Supplemental materials are available for this article. Go to the publisher's online edition of Phosphorus, Sulfur, and Silicon and the Related Elements to view the free supplemental file.

ChemInform Abstract: Anthraquinone Microwave-Induced Synthesis in Dry Media in Domestic Ovens.

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

ChemInform Abstract: Microwave-Induced Synthesis of Hydrazones and Wolff-Kishner Reduction of Carbonyl Compounds.

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

ChemInform Abstract: Microwave-Induced Synthesis of Nitrogen-Mustard Derivatives.

ChemInform Abstract: Microwave-Induced Synthesis of Nitrogen-Mustard Derivatives.

Conventional- and microwave-induced synthesis of biologically active 1,4-dihydropyridine derivatives containing benzothiazolyl moiety

A series of N-(6-methoxybenzothiazolyl)-2,3,5,6-tetrasubstituted-4-(aryl)-1,4-dihydropyridines was synthesized by reaction of 2-amino-6-methoxybenzothiazole, aromatic aldehyde and active methylene compound in methanol by conventional as well as microwave irradiation (solvent free and solid support) methods. The microwave irradiation technique gives better yield and the reaction is complete in a very short period of time. Under microwave irradiation better yields are obtained in acidic alumina as compared to silica, neutral alumina, and basic alumina. All compounds were tested for antibacterial and antifungal activities and the results were compared with standard drugs. Entomological activities were also tested. The results showed that a change in substitution pattern in the 1,4-dihydropyridine derivatives causes marked effects on their antimicrobial activity.

Microwave-Induced Synthesis of 2-Aminoimidazolines Under Neat Conditions

2-Aminoimidazolines were synthesized by the nucleophilic substitution reaction of 2-methylmercapto-4,5-dihydroimidazole hydroiodide with various amine compounds under neat conditions.

Microwave-Induced One-Pot Facile Synthesis Of Thiazolo-Pyrimidines Using Silica Gel As Solid Support

Microwave-Induced One-Pot Facile Synthesis Of Thiazolo-Pyrimidines Using Silica Gel As Solid Support

A facile microwave-induced synthesis of heterocyclic compounds and a dialdehyde from a naturally occurring limonoid

Paniculatin (1) (6α-acetoxyazadirone), a naturally occurring meliacin, was subjected to chemical transformations under microwave irradiation to give heterocyclic compounds and also a dialdehyde derivative. These include 2-methyloxazolo[4,5-d]-1,2,20,21,22,23-hexahydropaniculatin (4), 2-methyloxazolo[4,5-d]-6α,7α-dihydroxy-1,2,20,21,22,23-hexahydropaniculatin (5) and the dialdehyde (9) derivative of paniculatin. These reactions give excellent yields in a very short time when carried out under microwave irradiation under solvent-free condition.

Microwave-Induced Synthesis of Aromatic Polyamides by the Phosphorylation Reaction

This paper reports an optimization of the Yamazaki–Higashi method of direct polyamidation from aromatic diacids and aromatic diamines. As a model reaction, the polycondensation between 4,4′-oxydianiline and isophthalic acid was studied in the presence of a phosphorylation agent and under microwave irradiation. This experimental study revealed that optimal results can be attained by using a great excess of pyridine as catalyst (pyridine-to-monomer ratio of 7), at moderate radiation intensity (200 W), and up to 25% (w/v) monomer concentration. Although the inherent viscosity achieved by microwave and by conventional heating was comparable, an exceptional reaction rate under microwave irradiation yielded a polyamide inherent viscosity of around 1 dL g–1 in only a few minutes.

Pyrimido[4,5-b]quinoline-2-thiol/ol: microwave-induced one-pot synthesis, DNA binding and cleavage studies

This article describes the synthesis of pyrimido[4,5-b]quinoline-2-thiol/ol (3a/3b) by microwave irradiation technique. The dynamic interaction of compounds with deoxyribonucleic acid (DNA) was investigated by absorption spectra, viscosity measurements, and thermal denaturation studies. Intrinsic binding constants (K b ) had values 3.1×106 for 3a and 2.3×105 for 3b. The proposed DNA binding mode supports the large enhancement in the relative viscosity of calf thymus (CT-DNA) on binding to compounds. Results suggest that 3a/3b can bind to CT-DNA by intercalation via the aromatic ring into the base pairs of DNA. Moreover, efficient DNA damage was observed on oxidative cleavage in the presence of 3a/3b.

Microwave-induced synthesis of new optically active and soluble polyamides containing pendent 4-(2-phthalimidiylpropanoylamino)benzoylamino-groups

An aromatic chiral diacid monomer, 5-[4-(2-phthalimidiylpropanoylamino)-benzoylamino]isophthalic acid was synthesized in five steps under conventional heating in high yield and purity. A series of soluble, thermally stable and optically active polyamides (PA)s containing pendent groups made of phthalimide, flexible L: -alanine and benzamide sequence have been successfully synthesized under microwave irradiation. Excellent yields and very short reaction time were the main characteristics of this method. The same polymerization reactions were also carried out by conventional thermal heating and the results are compared. The resulting PAs had inherent viscosity in the range of 0.50-0.79 dL g(-1). All of the these polymers are readily dissolved in various solvents such as N-methyl-2-pyrrolidinone, N,N-dimethylacetamide and N,N-dimethylformamide and showed glass-transition temperature above 200 degrees C. Thermogravimetric analysis demonstrated that the 10% weight-loss temperatures in nitrogen were 372 and 422 degrees C for selected two PAs. All of these polymers showed optical rotation which is due to successful insertion of L: -alanine in the structure of chiral diacid monomer.