Advances in Catalyst Systems for the Asymmetric Hydrogenation and Transfer Hydrogenation of Ketones

Hydrogenation of prochiral ketones using chiral transition-metal catalysts represents the cleanest way to access enantiomerically enriched secondary alcohols, which are important building blocks in fine chemicals synthesis. Despite excellent activity, selectivity and compatibility of metal complexes with variety of functional groups, no universal catalysts exist. In this article we summarize the advances in catalyst systems for the asymmetric homogenous and heterogenous hydrogenation of ketones that have been made in past decade. The development of catalysts is oriented in reaching as high as activity with low catalyst loadings, using “greener’’ conditions, and ensuring good recyclability of catalysts. Even though ruthenium complexes represent the largest part of the catalysts, other metals rapidly penetrate this field.     

A modified dual current mode control method with an adaptive current bandwidth

In this paper, a new adaptive dual current mode control method (ADCMC) is presented, being a result of the modification of existing dual current mode control (DCMC) by introducing an adaptive current bandwidth. The ADCMC offers several important advantages over DCMC, such as no peak‐to‐average error in the inductor current, better transient response of current loop, and improved line regulation. A detailed analysis of the proposed ADCMC is performed for three types of DC–DC power electronics converters: buck, boost, and non‐inverting buck–boost converter. The performances of the ADCMC are tested with simulations and experiments. The obtained results confirm the analysis and validity of the proposed ADCMC method. Copyright © 2015 John Wiley & Sons, Ltd.     

Photo-Chemically-Deposited and Industrial Cu/ZnO/Al2O3 Catalyst Material Surface Structures During CO2 Hydrogenation to Methanol: EXAFS,XANES and XPS Analyses of Phases After Oxidation,Reduction, and Reaction

Catalysis Letters - Industrial Cu/ZnO/Al2O3 or novel rate catalysts, prepared with a photochemical deposition method, were studied under functional CH3OH synthesis conditions at the set temperature...     

Prediction of particle size distribution of dronedarone hydrochloride in spiral jet mill using design of experiments

In pharmaceutical industry, micronization is used to achieve solubility enhancement through the increase in specific surface area, and finally improving the dissolution rate of the drug. Industrial application of micronization is mostly based on experience and trial and error method. This research deals with the micronization of dronedarone hydrochloride and the path for evaluation of characteristics of micronized drug. Micronization was performed in laboratory spiral jet mill and the samples were analyzed to determine particle size distribution, span of distribution, sphericity, shape, and specific surface area. Results were analyzed using analysis of variance and in terms of specific energy consumption. Paths for evaluation of particle size and span of distribution were proposed and good correlation between experimental and model results was achieved.     

MA‐NOTMP: A Triazacyclononane Trimethylphosphinate Based Bifunctional Chelator for Gallium Radiolabelling of Biomolecules

In the past few years, gallium‐68 has demonstrated significant potential as a radioisotope for positron emission tomography (PET), and the optimization of chelators for gallium coordination is a major goal in the development of radiopharmaceuticals. Methylaminotriazacyclononane trimethylphosphinate (MA‐NOTMP), a new C‐functionalized triazacyclononane derivative with phosphinate pendant arms, presents excellent coordination properties for ⁶⁸Ga (low ligand concentration, labelling at low pH even at room temperature). A “ready‐to‐be‐grafted” bifunctional chelating agent (p‐NCS‐Bz‐MA‐NOTMP) was prepared to allow ⁶⁸Ga labelling of sensitive biological vectors. Conjugation to a bombesin_(7–14) derivative was performed, and preliminary in vitro experiments demonstrated the potential of MA‐NOTMP in the development of radiopharmaceuticals. This new chelator is therefore of major interest for labelling sensitive biomolecules, and further in vivo experiments will soon be performed.     

Internalization and Accumulation in Dendritic Cells of a Small pH‐Activatable Glycomimetic Fluorescent Probe as Revealed by Spectral Detection

DC‐SIGN, an antigen‐uptake receptor in dendritic cells (DCs), has a clear role in the immune response but, conversely, can also facilitate infection by providing entry of pathogens into DCs. The key action in both processes is internalization into acidic endosomes and lysosomes. Molecular probes that bind to DC‐SIGN could thus provide a useful tool to study internalization and constitute potential antagonists against pathogens. So far, only large molecules have been used to directly observe DC‐SIGN‐mediated internalization into DCs by fluorescence visualization. We designed and synthesized an appropriate small glycomimetic probe. Two particular properties of the probe were exploited: activation in a low‐pH environment and an aggregation‐induced spectral shift. Our results indicate that small glycomimetic molecules could compete with antigen/pathogen for binding not only outside but also inside the DC, thus preventing the harmful action of pathogens that are able to intrude into DCs, for example, HIV‐1.     

Polyamide 6 composite fibers with incorporated mixtures of melamine cyanurate,carbon nanotubes,and carbon black

Polyamide 6 (PA6) composite filament yarns were produced by the simultaneous incorporation of melamine cyanurate (MeCy) with multiwalled carbon nanotubes (CNTs) and carbon black (CB) into a composite matrix in a melt-spinning process. The results show that the simultaneous incorporation of MeCy with CNTs or CB additives provided filaments with a uniform black color. Tensile analysis confirmed that a reinforcing effect was achieved when CB was used, whereas the CNTs induced a reducing effect on the filament tenacity. With regard to the burning behavior, the flame-retardant action of MeCy was preserved in the presence of CB but was significantly hindered when used in combination with CNTs. These results indicate that the mixture of MeCy and CB was much more compatible for the production of reinforced PA6 composite filaments with increased thermal stability and improved flame retardancy over those of the MeCy and CNTs. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47007.     

Synthesis and characterization of Co5Cr2(P2O7)4 - New pyrophosphate as a colouring substance

A new pyrophosphate(V) of the formula Co₅Cr₂(P₂O₇)₄ was obtained in the system Co₂P₂O₇–Cr₄(P₂O₇)₃ as a result of solid-state reactions taking place between different reactants. The new compound crystallizes in the orthorhombic system and belongs to the family of pyrophosphates of the general formula M₅²⁺M₂³⁺(P₂O₇)₄ and is probably isostructural with Fe₅²⁺Fe₂³⁺(P₂O₇)₄. Powder diffraction pattern, infrared spectrum and SEM image of the new compound were presented. As a new potential inorganic pigment, Co₅Cr₂(P₂O₇)₄ was tested for its thermal stability, particle size distribution and colour properties, which were studied both for powder and after introduction into organic matrix and leadless ceramic glaze. The colour of Co₅Cr₂(P₂O₇)₄ powder was defined as deep grey with the colour coordinates L*/a*/b* = 60.63/-1.42/-3.41 and according to the hue angle (h° = 247.39°) it belongs to the blue region. Co₅Cr₂(P₂O₇)₄, with its relatively high thermal stability (t _m = 1230 ± 10 °C) and appropriate colour properties, is a good candidate to be used as inorganic pigment for colouring of acrylic paints. In the case of leadless glaze, the obtained compound acts as a dye.