Enantioselective "organocatalysis in disguise" by the ligand sphere of chiral metal-templated complexes

Asymmetric catalysis holds a prominent position among the important developments in chemistry during the 20th century. This was acknowledged by the 2001 Nobel Prize in chemistry awarded to Knowles, Noyori, and Sharpless for their development of chiral metal catalysts for organic transformations. The key feature of the catalysts was the crucial role of the chiral ligand and the nature of the metal ions, which promoted the catalytic conversions of the substrates via direct coordination. Subsequently the development of asymmetric organic catalysis opened new avenues to the synthesis of enantiopure compounds, avoiding any use of metal ions. Recently, an alternative approach to asymmetric catalysis emerged that relied on the catalytic functions of the ligands themselves boosted by coordination to metal ions. In other words, in these hybrid chiral catalysts the substrates are activated not by the metal ions but by the ligands. The activation and enantioselective control occurred via well-orchestrated and custom-tailored non-covalent interactions of the substrates with the ligand sphere of chiral metal complexes. In these metal-templated catalysts, the metal served either as a template (a purely structural role), or it constituted the exclusive source of chirality (metal-centred chirality due to the spatial arrangement of achiral or chiral bi-/tridentate ligands around an octahedral metal centre), and/or it increased the Brønsted acidity of the ligands. Although the field is still in its infancy, it represents an inspiring combination of both metal and organic catalysis and holds major unexplored potential to push the frontiers of asymmetric catalysis. Here we present an overview of this emerging field discussing the principles, applications and perspectives on the catalytic use of chiral metal complexes that operate as "organocatalysts in disguise". It has been demonstrated that these chiral metal complexes are efficient and provide high stereoselective control in asymmetric hydrogen bonding catalysis, phase-transfer catalysis, Brønsted acid/base catalysis, enamine catalysis, nucleophilic catalysis, and photocatalysis as well as bifunctional catalysis. Also, many of the catalysts have been identified as highly effective catalysts at remarkably low catalyst loadings. These hybrid systems offer many opportunities in the synthesis of chiral compounds and represent promising alternatives to metal-based and organocatalytic asymmetric transformations

The role of crypto-currencies in the development of the global currency system

The world monetary system is in the process of transition to a new level of development under the influence of the process of financial globalization, economic integration, as well as the activation of electronic currencies turnover. In these conditions, it is necessary to understand the causes of the changes and their possible consequences. One of the possible options for the development of the world monetary system can be the use of crypto-currency as international money.peer-reviewe

Improving the methodological tools of market pricing in exhibition marketing

Purpose: The purpose of the study is to determine ways to improve the methodological pricing tools in exhibition marketing from market positions. Design/Methodology/Approach: The leading method of research is a systematic approach, which is used to substantiate the economic and mathematical model of the optimal market price of the exhibition area, which is set depending on the quality of the exhibition. In order to measure differences in the quality of exhibition events, authors proposed to use reference-exhibition benchmarking characterized by the best price / quality ratio. Findings: The results of the study form the methodological basis for improving pricing not only in the exhibition business, but also in other areas of business activity. This is possible if the goods (services) are produced in the conditions of a monopolistic competition, and the quality of an individual product (service) could be quantified in a conventional unit, which should be scientifically substantiated. Practical implications: This study is of practical value for both exhibition organizers and their participants. Using of expo-activities of the developed methodological tools of market pricing allows strengthening their competitive positions and increasing the profitability of exhibitions, if the optimal market price of the exposition calculated by the proposed method compensates the average total costs of the exhibition company. Originality/Value: The article substantiates the original conceptual approach to exhibition pricing, which is based on interaction marketing, benchmarking and extremely high price, which prevents the formation of demand from exhibitors, that is proposed to be called the alternative price. It becomes possible to provide a scientific basis for determining the optimal market price of the exhibition area, that maximizes the profit of the organizing company.peer-reviewe

The charge-assisted hydrogen-bonded organic framework (CAHOF) self-assembled from the conjugated acid of tetrakis(4-aminophenyl)methane and 2,6-naphthalenedisulfonate as a new class of recyclable Brønsted acid catalysts

The acid–base neutralization reaction of commercially available disodium 2,6-naphthalenedisulfonate (NDS, 2 equivalents) and the tetrahydrochloride salt of tetrakis(4-aminophenyl)methane (TAPM, 1 equivalent) in water gave a novel three-dimensional charge-assisted hydrogen-bonded framework (CAHOF, F-1). The framework F-1 was characterized by X-ray diffraction, TGA, elemental analysis, and 1H NMR spectroscopy. The framework was supported by hydrogen bonds between the sulfonate anions and the ammonium cations of NDS and protonated TAPM moieties, respectively. The CAHOF material functioned as a new type of catalytically active Brønsted acid in a series of reactions, including the ring opening of epoxides by water and alcohols. A Diels–Alder reaction between cyclopentadiene and methyl vinyl ketone was also catalyzed by F-1 in heptane. Depending on the polarity of the solvent mixture, the CAHOF F-1 could function as a purely heterogeneous catalyst or partly dissociate, providing some dissolved F-1 as the real catalyst. In all cases, the catalyst could easily be recovered and recycled

Epigenetic engineering shows H3K4me2 is required for HJURP targeting and CENP-A assembly on a synthetic human kinetochore

Here, centromeric histone marks on a human artificial chromosome are found to resemble the chromatin landscape in transcribed genes, and selective manipulation shows them to govern the incorporation of the centromere-specifying CENP-A histone variant