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Photocatalytic generation of nitrenes and radicals can be used to tune or even control their reactivity. Photocatalytic activation of sulfonyl azides leads to the elimination of N2 and the resulting reactive species initiate C−H activations and amide formation reactions. Here, we present reactive radicals that are generated from sulfonyl azides: sulfonyl nitrene radical anion, sulfonyl nitrene and sulfonyl amidyl radical, and test their gas phase reactivity in C−H activation reactions. The sulfonyl nitrene radical anion is the least reactive and its reactivity is governed by the proton coupled electron transfer mechanism. In contrast, sulfonyl nitrene and sulfonyl amidyl radicals react via hydrogen atom transfer pathways. These reactivities and detailed characterization of the radicals with vibrational spectroscopy and with DFT calculations provide information necessary for taking control over the reactivity of these intermediates. [ABSTRACT FROM AUTHOR]

The following text examines fief holding by women in the surviving charters from Saxony from about the 11th to the beginning of the 14th centuries. Specifically, these are the areas around Harz delimited by the five bishoprics of Meissen, Naumburg, Hildesheim, Halberstadt, and Merseburg. The basis for analysis is collections of charters from these dioceses supplemented by the collections of charters from the two most significant noble houses active in this area — the houses of Ascania and Welf. The selection of sources and region is not a coincidence: It is probably where Eike von Repgow lived most of his life and wrote his Saxon Mirror (Sachsenspiegel), which significantly influences the modern study of medieval law. Through an analysis of the terminology associated with fiefs and feudal institutions in general, as well as through specific examples of fief holding by women, this study attempts to show that the limitations on a woman holding a fief as defined by Eike in the Saxon Mirror and largely accepted in the contemporary literature are not entirely consistent with the testimony of these diplomatic sources. [ABSTRACT FROM AUTHOR]

Flavin‐based catalysts are photoactive in the visible range which makes them useful in biology and chemistry. Herein, we present electrospray‐ionization mass‐spectrometry detection of short‐lived intermediates in photooxidation of toluene catalysed by flavinium ions (Fl+). Previous studies have shown that photoexcited flavins react with aromates by proton‐coupled electron transfer (PCET) on the microsecond time scale. For Fl+, PCET leads to FlH.+ with the H‐atom bound to the N5 position. We show that the reaction continues by coupling between FlH.+ and hydroperoxy or benzylperoxy radicals at the C4a position of FlH.+. These results demonstrate that the N5‐blocking effect reported for alkylated flavins is also active after PCET in these photocatalytic reactions. Structures of all intermediates were fully characterised by isotopic labelling and by photodissociation spectroscopy. These tools provide a new way to study reaction intermediates in the sub‐second time range. [ABSTRACT FROM AUTHOR]

Flavin‐based catalysts are photoactive in the visible range which makes them useful in biology and chemistry. Herein, we present electrospray‐ionization mass‐spectrometry detection of short‐lived intermediates in photooxidation of toluene catalysed by flavinium ions (Fl+). Previous studies have shown that photoexcited flavins react with aromates by proton‐coupled electron transfer (PCET) on the microsecond time scale. For Fl+, PCET leads to FlH.+ with the H‐atom bound to the N5 position. We show that the reaction continues by coupling between FlH.+ and hydroperoxy or benzylperoxy radicals at the C4a position of FlH.+. These results demonstrate that the N5‐blocking effect reported for alkylated flavins is also active after PCET in these photocatalytic reactions. Structures of all intermediates were fully characterised by isotopic labelling and by photodissociation spectroscopy. These tools provide a new way to study reaction intermediates in the sub‐second time range. [ABSTRACT FROM AUTHOR]

Photokatalytische Reaktionen, die einen reduktiven radikal‐polaren Übergang (RRPCO) beinhalten, erzeugen Intermediate mit carbanionischer Reaktivität. Viele dieser postulierten Intermediate entsprechen hochreaktiven metallorganischen Verbindungen. Die Bedingungen für ihre Bildung werden im Allgemeinen jedoch von ihren isolierten metallorganischen Analoga nicht toleriert und häufig wird eine andere Reaktivität beobachtet. Unsere Untersuchungen zu ihrer Natur und Reaktivität unter den üblichen photokatalytischen Bedingungen zeigen auf, dass diese Intermediate in der Tat als freie, superbasische Carbanionen beschrieben werden können, die in der Lage sind, gängige polare Lösungsmittel wie Acetonitril und Dimethylsulfoxid zu deprotonieren, die normalerweise als inert gelten. Ihre Basizität, nicht nur gegenüber Lösungsmitteln, sondern auch gegenüber Elektrophilen wie Aldehyden, Ketonen und Estern, ist vergleichbar mit der Reaktivität von isolierten Carbanionen in der Gasphase. Zuvor erfolglose Reaktionen, von denen man annahm, dass sie aus mangelnder Reaktivität resultieren, lassen sich durch ihre hohe Reaktivität gegenüber dem Lösungsmittel und schwach aciden Protonen der Reaktionspartner erklären. Dies liefert eine intuitive Erklärung für das Verhalten von photokatalytisch erzeugten Carbanionen, die es ermöglicht, Reaktionsmechanismen zu verifizieren, bei denen ein RRPCO‐Schritt vermutet wird, und erlaubt eine Abschätzung des synthetischen Anwendungsbereiches. [ABSTRACT FROM AUTHOR]

Photocatalytic reactions involving a reductive radical‐polar crossover (RRPCO) generate intermediates with carbanionic reactivity. Many of these proposed intermediates resemble highly reactive organometallic compounds. However, conditions of their formation are generally not tolerated by their isolated organometallic versions and often a different reactivity is observed. Our investigations on their nature and reactivity under commonly used photocatalytic conditions demonstrate that these intermediates are indeed best described as free, superbasic carbanions capable of deprotonating common polar solvents usually assumed to be inert such as acetonitrile, dimethylformamide, and dimethylsulfoxide. Their basicity not only towards solvents but also towards electrophiles, such as aldehydes, ketones, and esters, is comparable to the reactivity of isolated carbanions in the gas‐phase. Previously unsuccessful transformations thought to result from a lack of reactivity are explained by their high reactivity towards the solvent and weakly acidic protons of reaction partners. An intuitive explanation for the mode of action of photocatalytically generated carbanions is provided, which enables methods to verify reaction mechanisms proposed to involve an RRPCO step and to identify the reasons for the limitations of current methods. [ABSTRACT FROM AUTHOR]

The amphiphilic flavin derivatives 1,10-ethylene-bridged 3-alkylalloxazinium salts (alkyl=butyl, octyl, dodecyl and hexadecyl) were shown to catalyse the chemoselective oxidation of sulfides to sulfoxides with hydrogen peroxide in chloroform/water or dichloromethane/water systems. The efficiency of the catalytic oxidation depended substantially on the pH of the aqueous phase to reach maximum values at pH 7. Under such conditions, the complete conversion of aliphatic and aromatic sulfides occurred within a maximum of 24 h, whereas the non-catalysed reaction gave only traces of products. This new concept of two-phase oxidation utilises the activation and the increase in the lipophilicity of hydrogen peroxide by its covalent bonding to the alloxazinium catalyst. A practical application in the synthesis of modafinil was demonstrated. [ABSTRACT FROM AUTHOR]

Dies schließt eine Lücke im Verständnis photochemischer Katalysezyklen. Einblicke in die Reaktionsmechanismen der Nukleation und die Diagnose von Zink-Brom-Batterien, wobei sie sich auch auf die Visualisierung der Bildung von Polybromiden auf einer Pt-Oberfläche mittels Dunkelfeldmikroskopie stützen. H. Pei et al. präsentieren in ihrem Forschungsartikel auf S. 15594 eine autonome DNA-Nanomaschine für die Hochdurchsatzdetektion multipler Bakterienphänotypen in Blutproben. [Extracted from the article]

Sulfoxides (II) are synthesized by two-phase oxidation of sulfides (I) with hydrogen peroxide using a bridged flavinium salt as catalyst. [ABSTRACT FROM AUTHOR]

LDM COMPACT is a methodology, which permits the development of highly efficient combustion concepts for non-natural gas (NNG) engines without extensive testing on a multi-cylinder engine as well as tailor-made engine solutions for the special characteristics of NNG (LDM stands for LEC Development Methodology). Starting with a description of the baseline LDM, which incorporates the general approach for efficient engine development, this paper introduces the improved approach of LDM COMPACT and outlines each of the required steps, i.e., the preselection and basic design of essential engine parameters based on simulation, fundamental experiments on special test rigs, and experimental optimization of the concept on a single cylinder research engine. The fundamentals and main innovative features of the methodology are discussed. Two recent development projects (combustion of blast furnace gas and combustion of flare gases) are provided as examples of its application. In these examples, extensive use of simulation to evaluate different engine configurations permitted a significant share of optimization work to be completed in advance. The pre-optimized concepts were tested and validated on a single cylinder research engine. By applying LDM COMPACT, it was possible to develop the combustion concepts in a short amount of time and implement them into the multi-cylinder engine directly on-site. [ABSTRACT FROM AUTHOR]