Enantioselective Addition of Diethylzinc to Aromatic Aldehydes Catalyzed by Pyrolidine and Piperidine β-Amino Alcohols

The enantioselective alkylation of aryl aldehydes by diethylzinc in the presence of catalytic amounts of several chiral pyrolidine- and piperidine-based amino alcohol ligands, synthesized from the reaction of (R)-2-amino-1-butanol and (S)-2-amino-3-phenylpropan-1-ol with appropriate dibromoalkanes, was studied. The influence of temperature and ligand structure has been investigated. Addition of diethylzinc to aromatic aldehydes under the optimized condition gave the corresponding products in excellent yields with ee values of up to 77%.     

A lupane triterpenoid and other constituents of Salvia eremophila

Phytochemical investigation of the aerial parts of Salvia eremophila led to the isolation of a lupane triterpenoid, 3β, 20-dihydroxylupane-28-oic acid (1), together with eight other compounds, comprising three diterpene, two triterpene, two flavonoids and a steroidal glucoside. Their structures were elucidated by interpretation of their one-dimensional and two-dimensional NMR spectra and completed by the analysis of the HRESIMS data. Compounds 1, 2-4 and 8 were evaluated for their cytotoxicities against five human tumour cell lines. Compounds 1 and 3 hold a good potential for use in future studies due to their anti-cancer properties.     

Dynamic heat and moisture transfer in bulky PAN nanofiber mats

In this study a non-conventional electrospinning technique was designed for the production of high bulky polyacrylonitrile (PAN) nanofiber mats. Optimum nanofiber mats are achieved with 15 wt.% solution of PAN in dimethylformamide. Such mats result in a bulk porosity which is as high as 99.9 and a density as low as 0.84 × 10⁻³ g/cm³. The effect of the porosity of nanofiber mats on the air permeability and coupled heat and moisture transfer of fibers was investigated. Based on the results, high bulky nanofiber mats possess high heat and moisture transfer. Experimental data reveal that upon a slight decrease in the bulk porosity, air permeability and heat transfer decrease noticeably, while moisture transfer variation is low.     

Synthesis and Computational Study of Phosphorus Ionic Liquids

The synthesis of six tetraalkylammonium bromopentachlorophosphoride ionic liquids (ILs) is reported here. Their structures were determined by IR, ¹H NMR, and ¹³C NMR spectroscopy. Moreover, thermogravimetric (TG) and differential thermal analysis (DTA) were used to investigate the thermal behavior of these compounds. The results show that these ILs have excellent thermal stability below 145°C, and by decreasing the size of the alkyl groups, the thermal stabilities will increase. Along with the experimental study, these compounds have been studied computationally at the B3LYP/LANL2DZ level of theory using the PC GAMESS/Firefly program package. From these calculations, optimized geometries, molecular parameters, and vibrational spectra of ILs have been calculated. In addition, calculated frequencies are compared with the experimental frequencies after correction by the appropriate scaling factor. This comparison shows that our theoretical data are in good agreement with the experimental results.

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.     

Enhanced synchronous spectrofluorimetric determination of aflatoxin B1 in pistachio samples using multivariate analysis

The determination of aflatoxin B₁ (AFB1) in pistachio has been accomplished by normal and synchronous fluorimetry in combination with some multivariate calibration methods and derivative techniques. Extending the two-dimensional synchronous fluorescence scan to a three-dimensional total synchronous fluorescence scan was used to obtain the optimized Δλ for AFB1 in pistachio sample. The methods are based on the enhanced fluorescence of AFB1 by β-cyclodextrine in 10% (v/v) methanol-water solution. Twenty-six pistachio samples containing AFB1 in the range 0-15 ppb were used as calibration set. Eighteen combinational methods were tested to make best model for prediction of AFB1 and finally best results obtained using a method based on synchronous fluorimetry in combination with multiple linear regressions (MLR). For concentrations ranging from 0 to 15 ppb of AFB1 in 22 pistachio samples as prediction set, the values of root mean square difference (RMSD) and relative error of prediction (REP) using MLR were 0.328 and 4.453%, respectively were observed. Two naturally contaminated pistachio samples were analyzed by synchronous fluorimetry using MLR and compared with HPLC results.     

Finding susceptible areas for a 50 MW solar thermal power plant using 4E analysis and multiobjective optimization

Journal of Thermal Analysis and Calorimetry - In the present study, a power plant design was first carried out using thermo flow software. Energy, exergy, economic, environmental, and economic (4E)...     

Ring-opening (co)polymerization of cardanol glycidyl ether

The anionic ring-opening copolymerization of commercially available bio-based cardanol glycidyl ether (CGE) was investigated without any prior purification. As a first step, anionic-ring-opening homopolymerization was attempted through active chain-end and monomer-activated mechanisms. Both strategies were unsuccessful. Conversely, in a second step, the anionic alternating ring-opening copolymerization (AAROP) of CGE with the renewable N-acetyl homocysteine thiolactone (NHTL) was successfully carried out in the presence of a strong base. Anisole, a solvent classified as sustainable and rarely used in anionic ring-opening polymerization, proved to be a suitable for the AAROP. This polymerization is an unusual example of synthesis of linear polyesters with cardanol-based monomers. The copolymers were carefully characterized by ¹H, ¹³C, COSY, HSQC, ¹H-¹⁵N NMR and MALDI-ToF, demonstrating an alternating structure. Then, CGE was copolymerized with NHTL and another additional epoxide. The cardanol-derived monomers enable the preparation of functionalizable poly(ester-alt-thioether) bearing multiple allyl and alkene groups. The AAROP method in anisole offers new opportunity for green anionic polymerization through the use of sustainable chemicals, witnessed by the valorization of cardanol-derived compounds and expands the scope of synthesized renewable polyesters.     

Suppression of harmonic perturbations and bifurcation control in tracking objectives of a boiler–turbine unit in power grid

In the presence of harmonic disturbances, boiler–turbine units may demonstrate quasi-periodic behaviour due to the occurrence of various types of bifurcation. In this article, a nonlinear model of boiler–turbine unit is considered in which drum pressure, electric output and drum water level are controlled via manipulation of valve positions for fuel, steam and feed-water flow rates. For bifurcation control in tracking problem, two controllers are designed based on gain scheduling and feedback linearization (FBL). To investigate the efficiency of control strategies, three cases are considered for desired tracking objectives (a sequence of steps, ramps/steps, and a combination of them). According to the results, FBL controller works successfully in suppression of harmonic perturbations and consequently bifurcation control. As it is implemented, quasi-periodic solutions (caused by Hopf bifurcation) are vanished; leading to the appearance of periodic solutions with low amplitudes. Consequently, appropriate tracking performance with less oscillatory behaviour is observed for the drum pressure, electric output, and drum water level (desirable for the power grid). In addition, when FBL controller is used, less control efforts are predicted for the bifurcation control.     

Amberlyst-15 as a recyclable heterogeneous catalyst for synthesis of N-tert-butylamides via Ritter-type reaction

Highly efficient method for the preparation of N-tert-butylamides by reaction of nitriles with tert-butylacetate is described using Amberlyst-15 as a recyclable heterogeneous catalyst.Selective amidation of benzonitrile in the presence of acetonitrile was also achieved.