Studies on synthesis of quinonylidene Hoveyda‐type complexes

In a quest of redox‐switchable metathesis catalysts we attempted synthesis of ruthenium quinonylidene complexes using two synthetic pathways. First, Hoveyda‐type complexes bearing chelating benzylidene and naphthylidene ligands substituted with two alkoxy/hydroxy groups were synthesized and characterized. The catalysts were tested in model ring‐closing metathesis reactions, and displayed interesting correlations between structure and catalytic activity. Unfortunately, numerous attempts at oxidation of the complexes to derivatives of benzo‐ and naphthoquinone were unsuccessful. However, the second approach, using exchange reaction of ruthenium precursor with vinylquinone ligand, gave a transient unstable product observed with ¹H NMR. The experimental data suggest that conjugation of electron‐deficient quinones to the ruthenium centre results in intrinsically unstable species, which undergo secondary reactions under ambient conditions. Copyright © 2015 John Wiley & Sons, Ltd.     

Modification of MgO as an immobilizing agent for molten electrolyte

This paper describes the synthesis and texture of the MgF₂-MgO system used as an immobilizing agent of the electrolyte (KCl-LiCl-RbCl) for high-temperature cells. Preparations containing 20 and 40 mol% MgF₂ were characterized by a mesoporous structure and large specific surface areas. It was demonstrated that pellets containing 40–50 mas.% of MgF₂-MgO immobilizing agent were good electrolyte immobilizers. The ionic conductivity of pellets investigated in this work ranged from 0.02 to 0.04 S/cm, and it was about 20 times lower than the value set for the pure electrolyte. The difference is due to the tortuosity of the pellet. This mixture remains dimensionally stable at 400 °C and under 60 kPa and reveals good ionic conductivity during tests in a model cell with a 1.32-Ω resistor. During the discharge of the cell, it was observed that the voltage was not less than 1.5 V and current more than 1 A for approximately 100 s. No leakage of the electrolyte was observed.     

Biomolecular Assemblies Combining Two Orthogonal Copper‐Mediated Ligations in a One‐Pot Reaction

The access to multifunctional biomolecular compounds involves multistep reactions usually with a complicated protection scheme and lengthy separation processes. The development of a strategy combining several orthogonal ligations is highly desirable. Herein, we introduce a new method that involves two orthogonal copper‐mediated ligations of azide with alkyne, and amine with thioacid. We established compatible conditions to carry out molecular assemblies of three different chemical components in a single one‐pot reaction. The effectiveness of the method was demonstrated in the synthesis of biomolecular compounds that are known to target tumor tissue. The simple reaction conditions suggest that this strategy of combining several orthogonal ligations could have wide potential for the chemical synthesis of complex macromolecules.     

Obtaining aliphatic branched polycarbonates via simple copolymerization of trimethylene carbonate with cyclic carbonate containing pendant ester groups

Different possibilities for obtaining branched, functional carbonate copolymers are presented in this study. Copolymers were synthesized according to the ring‐opening polymerization (ROP) of the cyclic carbonate monomers, containing pendant ester groups. As an example, we chose copolymerization of ethyl 5‐methyl‐2‐oxo‐1,3‐dioxane‐5‐carboxylate (MTC‐Et) with trimethylene carbonate (TMC), using zinc (II) and lanthanum (III) acetylacetonates as ROP initiators. The transesterification processes of ester groups in pendant, short chains, appearing during conducted copolymerization, led to the establishment of two different fractions: first‐branched and high molecular weight fraction and second‐linear and low molecular weight. The content of this high‐molecular‐weight fraction increased with both: the amount of MTC‐Et in started reaction mixture and the time of conducted copolymerization. Reactivity constants in studied reaction were determined. It was possible to obtain the copolymer fraction (ca. 30%) with molecular weight of up to a million g/mol, with a highly branched chain microstructure using lanthanum (III) acetylacetonate as initiator. Conclusions were based on detailed NMR analysis, determining microstructure of the copolymer chains and additionally on GPC and DSC measurement. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55, 808–819     

Study of the Chromatographic Behavior of Selected Steroid Hormones on Aluminum Oxide Plates Based on Quantitative Structure—Retention Relationships

JPC – Journal of Planar Chromatography – Modern TLC - The chromatographic properties of eight steroids: trans-androsterone, methyltestosterone, testosterone, progesterone, cortisone,...