Silica supported sodium hydrogen sulfate(NaHSO4/SiO2): A mild and efficient reusable catalyst for the synthesis of aryl-14-H-dibenzo[a,j]xanthenes under solvent-free conditions

A simple and efficient procedure for the preparation of aryl-14-H-dibenzo[a,j]xanthenes by a one-pot condensation reaction of 2-naphthol and aryl aldehydes,in the presence of silica supported sodium hydrogen sulfate(NaHSO_4/SiO_2)as a catalyst and in the absence of solvent has been developed.The present method offers several advantages such as excellent yields,short reaction time (10-30 min),mild condition,simple work-up,and the use of a cheap and environmentally friendly catalyst with remarkable reusability.     

Silver-catalyzed one-pot synthesis of arylnaphthalene lactones

Arylnaphthalene lignan lactones are valuable natural products with promising anticancer and antiviral properties. In an effort to simplify their synthesis, we investigated a one-pot multicomponent coupling reaction between phenylacetylene, carbon dioxide, and 3-bromo-1-phenyl-1-propyne. After the corresponding 1,6-diyne was generated in situ, cyclization afforded the desired product. The level of regioselectivity was enhanced through the tuning of electronic properties. The use of cinnamyl bromide which led to the formation of a 1,6-enyne intermediate was also studied.     

Complexes of some tervalent metals with <Emphasis Type="Italic">N</Emphasis>-alkyl(benzyl)nitrozohydroxylamine derivatives

Twenty two new complexes of some tervalent metals (aluminum, chromium, iron, and lanthanides) with nitrozohydroxylamine N-alkyl(benzyl) derivatives ML₃^m · nH₂O, (m = 1?5) were synthesized and isolated in a crystalline state. The crystal and molecular structures of the iron(III) complex with N-(2-fluorobenzyl)-N-nitrozohydroxylamine were determined by X-ray diffraction. An octahedral coordination of the central ion and a bidentate chelating coordination of the organic ligand were established. The spectral criteria of coordination of nitrozohydroxylamine alkyl(benzyl) derivatives were determined, and the complexation processes in solutions were studied.     

Conformational and structural study of N-nicotinyl N′, N″-bis(diisobutyl amine)phosphoric triamide

Single crystals of C5H4NC(O)NHP(O)[N(i-C4H9)2]2 were prepared and investigated by X-ray crystallography. Interestingly, four symmetrically independent conformers were detected in the structure of this compound by X-ray crystallography. The greatest difference in these conformers was different torsion angles. In all conformers, the phosphoryl and carbonyl groups showed anti-configurations, and the two terminal CH3 groups of each alkyl chain in amine parts have different spatial orientations due to their connection to a prochiral carbon atom. The diastereotopic protons of every CH2 moiety in amine groups also have different spatial orientations. Every conformer forms a centrosymmetric dimer with its own symmetrically generated analog via a hydrogen bond. The first conformer connects to others (A, B, and C) via electrostatic interactions and forms a tetramer. All hydrogen bonds and electrostatic interactions result in the formation of a three-dimensional polymeric network in the crystalline lattice of compound. To find the most stable conformer, density functional theory (DFT) calculations were performed. The computationally optimized geometric parameters are in good agreement with the experimental results. According to DFT calculations, B is the most stable conformer with energy of ?987714.07 kcal/mol. In all conformers the electron density of HOMO is localized on P=O and C=O oxygen atoms and some parts of amine groups, while LUMO is localized on the nicotinamide part of the molecule.     

Development of agricultural biotechnology and biosafety regulations used to assess the safety of genetically modified crops in Iran

Rapid progress in the application of biotechnological methodologies and development of genetically modified crops in Iran necessitated intensive efforts to establish proper organizations and prepare required rules and regulations at the national level to ensure safe application of biotechnology in all pertinent aspects. Practically, preparation of a national biotechnology strategic plan in the country coincided with development of a national biosafety framework that was the basis for the drafted biosafety law. Although biosafety measures were observed by researchers voluntarily, the establishment of national biosafety organizations since the year 2000 built a great capacity to deal with biosafety issues in the present and future time, particularly with respect to food and agricultural biotechnology.     

Synergistic effect of silica nanoparticles and charged surfactants in the formation and stability of submicron oil-in-water emulsions

The influence of hydrophilic silica nanoparticles on the emulsification of a triglyceride oil (Miglyol812) in the presence of charged surfactants (lecithin or oleylamine) and the long term stability of the resultant oil-in-water emulsions are reported. A synergistic effect of nanoparticles and surfactants in improving emulsification and stability to coalescence is evident only when the silica nanoparticles are initially added to the oil phase. When nanoparticles are included from the water phase, no synergistic stabilisation was observed due to electrostatic bridging or unfavourable attachment due to the repulsive electrostatic and hydration forces. Free energies of adsorption for silica nanoparticles at the oil-water interface calculated from experimentally determined interfacial tensions and three phase contact angles can be correlated to long-term emulsion stability only when silica is added from oil phase.     

Efficient one-pot synthesis of novel 6′,9′-dihydro-2H,7′H-spiro[pyrimidine-5,8′-[1,3]dioxolo[4,5-f]quinoline]-2,4,6(1H,3H)-trione derivatives under mild and “green” reaction conditions

In this paper, an efficient method is introduced for the synthesis of 7′,9′-disubstituted 6′,9′-dihydro-2H,7′H-spiro[pyrimidine-5,8′-[1,3]dioxolo[4,5-f]quinoline]-2,4,6(1H,3H)-trione derivatives under mild and “green” reaction conditions. The method is based on one-pot multicomponent reaction of an aldehyde, barbituric acid, and benzo[d][1,3]dioxol-5-amine in ethanol as a green and environmentally friendly solvent. The reaction has given the products in the highest isolated yield in the presence of acetic acid as catalyst under reflux conditions. Various aldehydes, bearing electron-donating or -withdrawing functionalities have been used under the optimized conditions and successfully gave the desired products (13 examples) in high isolated yields.     

Interactions of hydrophilic silica nanoparticles and classical surfactants at non-polar oil-water interface

The interfacial and bulk properties of submicron oil-in-water emulsions simultaneously stabilised with a conventional surfactant (either lecithin or oleylamine) and hydrophilic silica nanoparticles (Aerosil?380) were investigated and compared with emulsions stabilised by either stabiliser. Emulsions solely stabilised with lecithin or oleylamine showed poor physical stability, i.e., sedimentation and the release of pure oil was observed within 3 months storage. The formation and long-term stability of silica nanoparticle-coated emulsions was investigated as a function of the surfactant type, charge, and concentration; the oil phase polarity (Miglyol?812 versus liquid paraffin); and loading phase of nanoparticles, either oil or water. Highly stable emulsions with long-term resistance to coalescence and creaming were formulated even at low lecithin concentrations in the presence of optimum levels of silica nanoparticles. The attachment energy of silica nanoparticles at the non-polar oil-water interface in the presence of lecithin was significantly higher compared to oleylamine in line with good long-term stability of the former compared to the sedimentation and release of oil in the latter. The attachment energy of silica nanoparticles at the polar oil-water interface especially in the presence of oleylamine was up to five-times higher compared to the non-polar liquid paraffin. The interfacial layer structure of nanoparticles (close-packed layer of particle aggregates or scattered particle flocs) directly related to the free energy of nanoparticle adsorption at both MCT oil and liquid paraffin-water interfaces.     

Spectroscopic studies of dactinomycin and vinorelbine binding to deoxyribonucleic acid and chromatin

Dactinomycin and vinorelbine are anticancer drugs, widely used as chemotherapeutic agents for the treatment of various cancers. This study represents an attempt to compare the effect of these drugs on DNA and soluble chromatin employing UV/vis, fluorescence and circular dichroism spectroscopy techniques. The results demonstrated that the absorbance at 260 and 210 nm was decreased and quenching of drugs with DNA and chromatin chromospheres induced reduction of fluorescence emission intensity. Circular dichroism profiles showed that the binding of drugs induced structural changes in both positive and negative extremes of DNA and chromatin revealing release or displacement of histone proteins from chromatin upon dactinomycin binding whereas vinorelbine preceded the chromatin into compaction. The results suggest that dactinomycin shows higher affinity to DNA compared to chromatin, whereas, vinorelbine recognizes the chromatin structure with higher affinity than free DNA. Also chromatin proteins play a fundamental role in drug-chromatin complex process.     

A Simple,Mild and Efficient One‐Pot Synthesis of 2‐Substituted Benzimidazoles in the Presence of H2O2/HCl under Microwave Irradiation

A simple, fast and efficient method for the preparation of several 2‐substituted benzimidazole derivatives is reported. Compounds were synthesized through a rapid one‐pot synthesis via microwave irradiation, starting from aldehydes and o‐phenylenediamine, in the presence of H₂O₂/HCl system in acetonitrile. The significant features of this method are short reaction times, high yields, easy and quick isolation of the products.