A new, efficient, and simple method for the synthesis of thiiranes from epoxides under solvent-free conditions

A simple, efficient, and new method has been developed for the synthesis of thiiranes from epoxides through a one-pot reaction of epoxides with diethyl phosphite in the presence of ammonium acetate or ammonium hydrogen carbonate/sulfur/ and acidic alumina under solvent-free conditions using microwave irradiation.     

A new design of the elimination and choice translating reality method for multi-criteria group decision-making in an intuitionistic fuzzy environment

The purpose of this paper is to design a new extension of the ELECTRE, known as the elimination and choice translating reality method, for multi-criteria group decision-making problems based on intuitionistic fuzzy sets. This method is widely utilized when a set of alternatives should be identified and evaluated with respect to a set of conflicting criteria by reflecting decision makers’ (DMs’) preferences. However, handling the exact data and numerical measure is difficult to be precisely focused because the DMs’ judgments are often vague in real-life decision problems and applications. A more realistic and practical approach can be to use linguistic variables expressed in intuitionistic fuzzy numbers instead of numerical data to model DMs’ judgments and to describe the inputs in the ELECTRE method. The proposed intuitionsitic fuzzy ELECTRE utilizes the truth-membership function and non-truth-membership function to indicate the degrees of satisfiability and non-satisfiability of each alternative with respect to each criterion and the relative importance of each criterion, respectively. Then, a new discordance intuitionistic index is introduced, which is extended from the concept of the fuzzy distance measure. Outranking relations are defined by pairwise comparisons and a decision graph is depicted to determine which alternative is preferable, incomparable or indifferent in the intuitionistic fuzzy environment. Finally, a comprehensive sensitivity analysis is employed to further study regarding the impact of threshold values on the final evaluation, and a comparative analysis is demonstrated with an application example in flexible manufacturing systems between the proposed ELECTRE method and the existing intuitionistic fuzzy technique for order preference by similarity to ideal solution (IF-TOPSIS) method.     

A quantile-based Time at Risk: A new approach for assessing risk in financial markets

In this paper, we provide a new measure for evaluation of risk in financial markets. This measure is based on the return interval of critical events in financial markets or other investment situations. Our main goal was to devise a model like Value at Risk (VaR). As VaR, for a given financial asset, probability level and time horizon, gives a critical value such that the likelihood of loss on the asset over the time horizon exceeds this value is equal to the given probability level, our concept of Time at Risk (TaR), using a probability distribution function of return intervals, provides a critical time such that the probability that the return interval of a critical event exceeds this time equals the given probability level. As an empirical application, we applied our model to data from the Tehran Stock Exchange Price Index (TEPIX) as a financial asset (market portfolio) and reported the results.     

Impregnated copper ferrite on mesoporous graphitic carbon nitride: An efficient and reusable catalyst for promoting ligand‐free click synthesis of diverse 1,2,3‐triazoles and tetrazoles

Magnetic CuFe₂O₄/g‐C₃N₄ hybrids were synthesized through a facile method and their catalytic performances were evaluated in click chemistry for the first time. The structural and morphological characterization of prepared materials was carried out by different techniques such as X‐ray diffraction, high‐resolution transmission electron microscopy, field emission scanning electron microscopy, Fourier infrared spectroscopy, vibrating sample magnetometry, thermogravimetric analysis, and N₂ adsorption–desorption analysis (Brunauer–Emmett–Teller surface area). The utilization of magnetic CuFe₂O₄/g‐C₃N₄ enabled superior performance in the one‐pot azide–alkyne cycloaddition reaction in water using alkyl halides and epoxides as azide precursors without the need of any additional agents. The present system is broad in scope and especially practical for the synthesis of macrocyclic triazoles and also tetrazoles. In addition, the catalytic system highly fulfills the demands of “green click chemistry” with its convenient conditions, especially easy access to a variety of significant products in low catalyst loading and simple work‐up and isolation procedure.     

Electrochemical platform for simultaneous determination of levodopa,acetaminophen and tyrosine using a graphene and ferrocene modified carbon paste electrode

Microchimica Acta - A carbon paste electrode (CPE) was modified with graphene and ethyl 2-(4-ferrocenyl-[1,2,3]triazol-1-yl) acetate (EFTA) and used for electrocatalytic oxidation of levodopa....     

Synthesis of MnAl2O4 nanocrystallites by Pechini and sequential homogenous precipitation methods: characterization, product comparison, photocatalytic effect, and Taguchi optimization

Nanocrystalline manganese aluminate (MnAl₂O₄) has been synthesized by Pechini and sequential homogenous precipitation methods and the results have been compared. The Taguchi L₄ statistical design was utilized to optimize the production of MnAl₂O₄ nanoparticles by Pechini method. The MnAl₂O₄ nanocrystallites obtained by Pechini and sequential homogenous precipitation methods had the average particle size of 26.5 and 49.5 nm, respectively. The products were characterized with X-ray diffraction, laser light scattering, thermogravimetry analysis, Fourier transform infrared, UV–visible, energy dispersive X-ray, scanning electron microscope and inductively coupled plasma analyses. The photocatalytic activities of MnAl₂O₄ nanoparticles synthesized by two methods were investigated using aqueous solution of methylene blue under irradiation of visible light.     

Inside-Needle Extraction Method Based on Molecularly Imprinted Polymer for Solid-Phase Dynamic Extraction and Preconcentration of Triazine Herbicides Followed by GC–FID Determination

An inside-needle extraction method was developed through thermal polymerization of atrazine-molecularly imprinted polymer (MIP) on the internal surface of a stainless steel hollow needle, which was oxidized and silylated. The fabricated coating (MIP layer) for the needle was durable and showed very good chemical and thermal stability. It could be mounted on a glass syringe and be directly coupled with gas chromatographic (GC) systems. The parameters being effective on the coating and extraction processes, namely nature of oxidizing agent, silylation time, nature and amount of porogen, template-to-MIP components ratio, polymerization time and temperature, sample volume, flow rate, pH and ionic strength of the sample were investigated and optimized. The extraction needle showed high selectivity as well as a great extraction capacity for triazines. The extraction of atrazine, simazine, cyanazine, ametryn, prometryn and terbutryn using the fabricated extraction needle and followed by GC analysis resulted in detection limits of 2.6, 21, 24, 32, 38 and 42 ng mL⁻¹, respectively. The fabricated needle proved to be applicable to the analysis of real samples by comparing the results obtained for non-spiked and spiked samples of grape juice, tap water and groundwater.

     

A mild and green chemistry approach for the synthesis of symmetrical spirooxindole derivatives

A simple and eco-friendly synthesis of the biologically important spirooxindole scaffold was done by the reaction of isatin with activated pyrazolones in the presence of a catalytic amount of p-toluenesulfonic acid in water at room temperature. A variety of symmetrical spirooxindole derivatives were obtained with excellent yields within short reaction time. This method is of great value because of its environmentally benign character, high yield, and easy handling.     

An efficient four-component synthesis of dithiocarbamate derivatives

An environmentally benign, one-pot, four-component synthesis of chemically and pharmaceutically interesting dithiocarbamate derivatives is reported. The one-pot reaction of various aromatic aldehydes, ketones, aliphatic amines, and carbon disulfide, in the presence of potassium hydroxide in urea-choline chloride deep eutectic solvent or ethanol, leads to the corresponding dithiocarbamates in good to excellent yields. This method provides a convenient and time-saving strategy, with a simple work-up procedure.