Magnetic‐based picolinaldehyde–melamine copper complex for the one‐pot synthesis of hexahydroquinolines via Hantzsch four‐component reactions

A picolinaldehyde–melamine copper complex was loaded on a magnetic Fe₃O₄ core, so that it contained 0.33 mmol of Cu per gram, and was used as an efficient catalyst. The as‐synthesized catalyst was characterized using various techniques, including Fourier transform infrared spectroscopy, X‐ray diffraction, energy‐dispersive X‐ray spectroscopy, field emission scanning electron microscopy, transmission electron microscopy, vibrating sample magnetometry and thermogravimetric analysis. The catalyst was used to activate the raw materials in the synthesis of hexahydroquinoline derivatives in one‐pot four‐component reactions. Low reaction time (minutes versus half an hour), solvent‐free condition and magnetically separable catalyst are some salient features of the developed catalyst. Also, the optimum amount of catalyst and temperature were determined as 0.07 g and 87.6 °C, respectively, which were obtained using response surface methodology and optimization techniques.     

Mizoroki–Heck and Suzuki–Miyaura reactions mediated by poly(2‐acrylamido‐2‐methyl‐1‐propanesulfonic acid)‐stabilized magnetically separable palladium catalyst

The purpose of this work was to synthesize and characterize a new magnetic polymer nanosphere‐supported palladium(II) acetate catalyst for reactions requiring harsh conditions. In this regard, an air‐stable, moisture‐stable and highly efficient heterogenized palladium was synthesized by the coordination of palladium(II) acetate with poly(2‐acrylamido‐2‐methyl‐1‐propanesulfonic acid)‐grafted modified magnetic nanoparticles with a core–shell structure. The structure of the newly developed catalyst was characterized using various techniques. The catalytic activity of the resultant nano‐organometallic catalyst was evaluated in Mizoroki–Heck and Suzuki–Miyaura reactions to afford the corresponding coupling products in good to excellent yields. High selectivity as well as outstanding turnover number (14 143, 4900) and turnover frequency (28 296, 7424) values were recorded for the catalyst in Suzuki–Miyaura and Mizoroki–Heck reactions, respectively. Magnetic separation and recycling of the catalyst for at least six runs became possible without any significant loss of efficiency or any detectable palladium leaching.     

Determination of the Heat Transfer Coefficient of Metal Oxide Based Water Nanofluids in a Laminar Flow Regime Using an Adaptive Neuro-Fuzzy Inference System

In order to enhance the thermal properties of turbine oil (TO), three different nanoparticles (CuO, Al₂O₃, and TiO₂) are loaded into the TO. To measure the thermal performance of nanoparticle-based TO nanofluids at laminar flow and under constant heat flux boundary conditions, an experimental setup was applied. The obtained data clearly demonstrate the positive effect of all nanoparticles on the heat transfer rate of TO. As the most important factor, the heat transfer coefficient of the abovementioned two-phase systems is increased upon increasing both the volume concentration and the flow rate. An adaptive neuro-fuzzy inference system (ANFIS) is applied for modeling the effect of critical parameters on the heat transfer coefficient of nanoparticle-TO based nanofluids numerically. The results are compared with experimental ones for training and test data. The results suggest that the developed model is valid enough and promising for predicting the extant of the heat transfer coefficient. R² and MSE values for all data were 0.990208751 and 108.1150734, respectively. Based on the results, it is obvious that our proposed modeling by ANFIS is efficient and valid, which can be expanded for more general states.     

Nanomagnetically modified vitamin B3 (Fe3O4@Niacin): An efficient and reusable green biocatalyst for microwave‐assisted rapid synthesis of 2‐amino‐3‐cyanopyridines in aqueous medium

Superparamagnetic nanoparticles of modified vitamin B₃ (Fe₃O₄@Niacin) represent a new, efficient and green biocatalyst for the one‐pot synthesis of 2‐amino‐3‐cyanopyridine derivatives via four‐component condensation reaction between aldehydes, ketones, malononitrile, and ammonium acetate under microwave irradiation in water. This new magnetic organocatalyst was easily isolated from the reaction mixture by magnetic decantation using an external magnet and reused at least six times without significant degradation in the activity. The catalyst was fully characterized by FT‐IR, XRD, SEM, VSM, UV–Vis, DLS and EDS. Excellent yield, very short reaction time (7–10 min), operational simplicity, easy work‐up procedure, avoidance of hazardous or toxic catalysts and organic solvents are the main advantages of this green methodology which makes it more economic than the other conventional methods.     

Green route for selective gram‐scale oxidation of sulfides using tungstate/triazine‐based ionic liquid immobilized on magnetic nanoparticles as a phase‐transfer heterogeneous catalyst

Tungstate ions were successfully loaded onto triazine‐based ionic liquid‐functionalized magnetic nanoparticles through an anion exchange process. The use of triazine core for creating ionic liquid led to the immobilization of high amounts of WO₄^2?. The resulting catalyst showed high activity and selectivity in the oxidation of sulfides to sulfoxides with H₂O₂ as a green oxidant at room temperature. In addition, due to the presence of ammonium groups in the catalyst structure, water dispersibility of the catalyst was increased. More important, the catalyst was magnetically recovered and reused for up to six runs without any marked decrease of activity and selectivity. Finally, easy gram‐scale oxidation of methylphenyl sulfide as well as fast separation of catalyst and product makes the protocol economical and industrially applicable.     

Calculation of optical and electronic properties of zinc sulfide produced thin layers under different deposition angles

Zinc sulfide nano layers were deposited on glass substrates at 300 K by physical vapor deposition method, under high vacuum conditions and different deposition angles. Thickness of the layers were measured 73 nm, by quartz crystal method. Optical reflectance and transmittance of the layers were measured in the wave length of 300?C1100 nm. Optical constants were calculated by Kramers-Kronig relations. The influence of deposition angle in optical properties of ZnS nano layers are investigated. By using Generalized Gradient Approximations in context of plane wave pseudo-potentials (norm conserving and Ultrasoft) and full-potential linearized augmented plane wave methods, Band structure calculated and compared with experimental results. Possible energy transitions are also reported.     

Preparation,characterization, and use of poly(vinylpyrrolidonium) hydrogen phosphate ([PVP-H]H2PO4) as a new heterogeneous catalyst for efficient synthesis of 2-amino-tetrahydro-4H-pyrans

Research on Chemical Intermediates - A novel Brønsted solid acid named poly(vinylpyrrolidonium) hydrogen phosphate ([PVP-H]H2PO4) has been prepared by using H3PO4 and poly(vinylpyrrolidone) as...