High‐grade periodate is relatively expensive, but is required for many sensitive applications such as the synthesis of active pharmaceutical ingredients. These high costs originate from using lead ...dioxide anodes in contemporary electrochemical methods and from expensive starting materials. A direct and cost‐efficient electrochemical synthesis of periodate from iodide, which is less costly and relies on a readily available starting material, is reported. The oxidation is conducted at boron‐doped diamond anodes, which are durable, metal‐free, and nontoxic. The avoidance of lead dioxide ultimately lowers the cost of purification and quality assurance. The electrolytic process was optimized by statistical methods and was scaled up in an electrolysis flow cell that enhanced the space–time yields by a cyclization protocol. An LC‐PDA analytical protocol was established enabling simple quantification of iodide, iodate, and periodate simultaneously with remarkable precision.
The electrochemical synthesis of periodate from iodide at boron‐doped diamond (BDD) anodes was developed, which in contrast to lead dioxide anodes are sustainable and durable. Toxic contaminations are hereby prevented, ultimately reducing the cost of purification. This opens the door for the broad application of periodate for demanding applications, such as the synthesis of active pharmaceutical ingredients.
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Li/MgO is one of the most frequently investigated catalysts for the oxidative coupling of methane. Besides catalytic testing, it is also a suitable system to perform surface science experiments and ...quantum chemical calculations, which is not possible for many other active catalysts. However, the real structure of Li/MgO, the nature of the active center and the structure - activity relationship remain unclear, despite all the research that has been done. The aim of this review is to summarize the available knowledge on Li/MgO to structure and accelerate and improve the ongoing work on this catalytic system.
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The synthesis of substituted 2-cyclopentenones using a commercially available gold(I) catalyst is described under flexible reaction conditions. During the course of our investigations, we discovered ...that using a proton source as an additive is required to obtain the desired substituted cyclopentenones in good yields.
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The synthesis of aurated phosphindolium complexes from easy accessible 1,5‐alkynylphosphine derivatives has been studied by using gold(I) complexes featuring carbene and phosphine ligands as ...initiators. Upon formation of the mixed phosphine NHC/phosphine gold species, elevated temperatures induced the cyclization to give stable aurated phosphindolium salts, which is supported by DFT calculations. The key elementary step that comprises a yet unknown anti‐phosphinoauration of an unactivated alkyne is favored if bulky NHC ligands are used which was analyzed by kinetic measurements. This concept could furthermore be extended to neutral (phosphindolium)AuCl complexes featuring the yet unknown phosphindole ligand.
Phosphinoauration: Aurated phosphindolium complexes are synthesized from ortho‐phosphane phenylacetylene derivatives by an anti‐phosphinoauration reaction. This new elementary step in gold catalysis is favored if bulky ligands are used at the gold center, which is in accord with the concept of Frustrated Lewis Pair (FLP) chemistry.
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A domino sequence, involving a phosphinoauration and a gold‐catalyzed 6‐endo‐dig cyclization step, was developed. Starting from modular and simple‐to‐prepare phosphadiynes, π‐extended ...phosphoniumfluorenes were synthesized. The mechanistic proposal was supported by kinetic measurements and by the trapping of key intermediates. These led to important conclusions for the gold‐catalyzed hydroarylation mechanism. Cyclic voltammetry (CV) and UV/Vis spectroscopy measurements indicated interesting properties for materials science. The phosphoniumfluorene structure was tested as a hole‐blocking layer in perovskite solar cells of inverted architecture. Devices with the phosphoniumfluorene exhibited an efficiency of 14.2 %, which was much higher than that of devices without (10.7 %).
On the block: A domino reaction to phosphoniumfluorenes in up to quantitative yields is developed. Mechanistic studies support the proposal of a gold‐exchange mechanism. The properties are investigated by various techniques. The material is tested as a hole‐blocking layer in perovskite solar cells. PCBM=6,6‐phenyl‐C61‐butyric acid methyl ester, PEDOT:PSS=poly(3,4‐ethylenedioxythiophene) polystyrene sulfonate, ITO=indium tin oxide.
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Common speech quality evaluation methods rely on self-reported opinions after perceiving test stimuli. Whereas these methods-when carefully applied-provide valid and reliable quality indices, they ...provide little insight into the processes underlying perception and judgment. In this paper, we analyze the performance of electroencephalography (EEG) for indicating different types of degradations in speech stimuli. We show that a certain EEG technique, event-related-potentials (ERP) analysis, is a useful and valid tool in quality research. Three experiments are reported which show that quality degradations can be monitored in conscious and presumably non-conscious stages of processing. Potential and limitations of the approach are discussed and lines of future research are drawn.
A fast and simplified synthesis of 1',2'-dideoxy-1'-pyrenyl-riboside and several other C-nucleosides is shown. Shelf-stable 1-O-methyl-3,5-di-O-toluoyl-2-deoxyribose is demonstrated to serve as a ...versatile glycosyl donor in Lewis acid promoted Friedel-Crafts alkylations of unsubstituted pyrene and other inexpensive arenes such as fluorene and methylnaphthalene. The reaction conditions favour the formation of beta-configurated C-nucleosides which renders additional epimerisation steps unnecessary. As a result, protected beta-aryl-C-nucleosides are available directly from non-substituted arenes in three steps overall.
An emerging interest for the application of periodate in the synthesis of active pharmaceutical ingredients (APIs) and for the valorization of renewable feedstock is eminent. However, periodate ...exhibits a high molecular mass, is expensive compared to other common bulk-oxidizers and is used only reluctantly in technical applications. Recently, a new and green electrochemical synthesis was established. The preparation and regeneration method for periodate lowers costs and enables the use of periodate in the synthesis of regulated products. This review will briefly introduce the key innovations in the electrochemical synthesis of periodate and will survey the most important applications of periodate in the production of fine chemicals.
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10.
Chemical Energy Storage Schlögl, Robert; Aho, Atte; Antonietti, Markus ...
2012, 2013-01-01
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Energy - in the headlines, discussed controversially, vital. The use of regenerative energy in many primary forms leads to the necessity to store grid dimensions for maintaining continuous supply and ...enabling the replacement of fossil fuel systems. This work provides a hands-on insight into the present status of energy conversion and deals with aspects of chemical energy storage considering the geosphere, electrochemistry, catalysis, synthesis of catalysts, functional analysis of catalytic processes and the interface between electrochemistry and heterogeneous catalysis. Robert Schlögl, Fritz-Haber-Institut derMax-Planck-Gesellschaft, Berlin, Germany.
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