Reactive & Efficient: Organic Azides as Cross-Linkers in Material Sciences

The exceptional reactivity of the azide group makes organic azides a highly versatile family of compounds in chemistry and the material sciences. One of the most prominent reactions employing organic azides is the regioselective copper(I)-catalyzed Huisgen 1,3-dipolar cycloaddition with alkynes yielding 1,2,3-triazoles. Other named reactions include the Staudinger reduction, the aza-Wittig reaction, and the Curtius rearrangement. The popularity of organic azides in material sciences is mostly based on their propensity to release nitrogen by thermal activation or photolysis. On the one hand, this scission reaction is accompanied with a considerable output of energy, making them interesting as highly energetic materials. On the other hand, it produces highly reactive nitrenes that show extraordinary efficiency in polymer crosslinking, a process used to alter the physical properties of polymers and to boost efficiencies of polymer-based devices such as membrane fuel cells, organic solar cells (OSCs), light-emitting diodes (LEDs), and organic field-effect transistors (OFETs). Thermosets are also suitable application areas. In most cases, organic azides with multiple azide functions are employed which can either be small molecules or oligo- and polymers. This review focuses on nitrene-based applications of multivalent organic azides in the material and life sciences

Lanthanide conjugates as versatile instruments for therapy and diagnostics

Lanthanides have demonstrated outstanding properties in many fields of research including biology and medicinal chemistry. Their unique luminescence and magnetic properties make them the metals of choice for next generation theranostics that efficiently combine the two central pillars of medicine – diagnostics and therapy. Attached to targeting units, lanthanide complexes pave the way for real-time imaging of drug uptake and distribution as well as specific regulation of subcellular processes with few side effects. This enables individualized treatment options for severe diseases characterized by altered cell expression. The highly diverse results achieved as well as insights into the challenges that research in this area has to face in the upcoming years will be summarized in the present review

An Intramolecular Iodine-Catalyzed C(sp3^{3})−H Oxidation as a Versatile Tool for the Synthesis of Tetrahydrofurans

The first iodine-catalyzed cyclization reaction of aliphatic primary and secondary alcohols gives access to tetrahydrofurans through an intramolecular C(sp$^{3}$)−H activation. The reaction proceeds under mild reactions using either a floodlight lamp or daylight. The formation of ubiquitous occurring tetrahydrofuran patterns has been extensively investigated in the 1960s as it was one of the first examples of a non-directed remote C−H activation. These approaches suffer from the use of toxic transition metals in overstoichiometric amounts. An attractive metal-free solution for transforming carbon-hydrogen bonds into carbon-oxygen bonds lies in applying economically and ecologically favorable iodine reagents. The presented method involves an intertwined catalytic cycle of a radical chain reaction and an iodine(I/III) redox couple by selectively activating a remote C(sp$^{3}$)−H bond under visible-light irradiation. The reaction proceeds under mild reaction conditions, is operationally simple and tolerates many functional groups giving fast and easy access to different substituted tetrahydrofurans

Metal‐to‐Metal Distance Modulation by Ligand Design: A Case Study of Structure‐Property Correlation in Planar Chiral Cyclophanyl Metal Complexes

Multinuclear metal complexes have seen tremendous progress in synthetic advances, their versatile structural features, and emerging applications. Here, we conceptualize Metal-to-Metal distance modulation in cyclophanyl metal complexes by bridging ligand design employing the co-facially stacked cyclophanyl-derived pseudo-geminal, -ortho, -meta, and -para constitutional isomers grafted with N-, O-, and P- containing chelates that allow the installation of diverse (hetero)metallic moieties in a distance-defined and spatially-oriented relation to one another. Metal-to-Metal distance modulation and innate transannular “through-space” π–π electronic interactions via the co-facially stacked benzene rings in cyclophanyl-derived complexes as well as their specific stereochemical structural features (element of planar chirality) are crucial factors that contribute to the tuning of structure-property relationships, which stand at the very center from the perspective of cooperative effects in catalysis as well as emerging material applications

До історії міста через історію його мешканців

Минулого року краєзнавча бібліотека Дніпропетровщини поповнилася унікальним у своєму роді виданням – такою собі «живою» історією Дніпродзержинська (колишнього Камя’нського), одного з найбільших міст нашої області. Автори книги «Дух минулої епохи» – відомий дніпродзержинський журналіст і публіцист Олександр Слоневський та один з кращих істориків міста Людмила Яценко, яка, на жаль, не дожила до виходу в світ їхнього спільного творіння. Справжній, не кон’юнктурний і незаіделогізований патріотизм та любов до своєї «малої батьківщини» відчуваються на кожній сторінці цього видання, яке з’явилося не з приводу чергового ювілею або пам’ятної дати, а стало результатом тривалої самовідданої роботи двох ентузіастів. До того ж книга О. Слоневського та Л. Яценко є першим поглядом на складну історію Кам’янського – Дніпродзержинська, відмінним від «канонічної» радянської версії

MANAGEMENT DECISION MAKING IN MARKETING

Miniaturized microreactors enable photochemistry with laser irradiation in flow mode to convert azidobiphenyl into carbazole with high efficiency

NMR Chemical Shift Ranges of Urine Metabolites in Various Organic Solvents

Signal stability is essential for reliable multivariate data analysis. Urine samples show strong variance in signal positions due to inter patient differences. Here we study the exchange of the solvent of a defined urine matrix and how it affects signal and integral stability of the urinary metabolites by NMR spectroscopy. The exchange solvents were methanol, acetonitrile, dimethyl sulfoxide, chloroform, acetone, dichloromethane, and dimethyl formamide. Some of these solvents showed promising results with a single batch of urine. To evaluate further differences between urine samples, various acid, base, and salt solutions were added in a defined way mimicking to some extent inter human differences. Corresponding chemical shift changes were monitored

Controlled, Stepwise Syntheses of Oligomers with Modified Quinoxaline Backbones

New oligomers based on quinoxaline units were successfully synthesized through multistep reactions using Wittig coupling, affording (E)-(quinoxalin-2-yl)ethene oligomers. Diverse quinoxaline-based phosphonium salts were designed and synthesized, enabling versatility and compatibility regarding the oligomer-building process. The characterization of the oligomers showed excellent stereoisomer specificity, i.e., a fully E-configurated conjugated π-system. The oligomers’ light absorption/emission profiles indicate potential properties for an application in materials science

Skeletal Editing—Nitrogen Deletion of Secondary Amines by Anomeric Amide Reagents

Late-stage modification is highly desirable for the diversification and modification of biologically active compounds. Peripheral editing (e.g., C−H activation) has been the predominant methodology, whereas skeletal editing is in its infancy. The single-atom N-deletion using anomeric amide reagents constitutes a powerful tool to modify the underlying molecular skeletons of secondary amines. N-pivaloyloxy-N-alkoxyamide is easily prepared on a large scale and promotes C−C bond formation in good yields under the extrusion of N2 for a variety of (cyclic) aliphatic amines. The exploitation of widely available amines allows the use of existing amine synthesis protocols to translate into the construction of new C−C bonds, enabling ring contraction and the potential for structure optimization of biologically active compounds

Towards the synthesis of calotropin and related cardenolides from 3-epiandrosterone: A-ring related modifications

Calotropin and related cardiac glycosides isolated from plants such as calotropis gigantea represent an interesting target for biological investigations and are based on a cardiac steroid that is doubly connected to a sugar moiety. This naturally occurring family of cardiac glycosides was not only reported to have similar cardiac properties as the drugs digitoxin and digoxin, but also show cytotoxic activity against several cancer cell lines. Herein, the first synthetic access to these molecules is reported highlighting the required transformations of the A-ring of the steroid when starting from commercially available and inexpensive 3-epiandrosterone. Our strategy is based on a regioselective C–H oxidation of the methyl group at C-17 delivering the 2α,3β-trans-diol moiety at the same time and ensuring its connection to the sugar unit