1,720,964 research outputs found
Photoinduzierte Ruthenium‐katalysierte C−H Arylierungspolymerisation bei Raumtemperatur
No full textAbstract Die Übergangsmetall‐katalysierte C−H Arylierungspolymerisation (CHAP) ist eine attraktive Strategie, um π‐konjugierte Polymere auf nachhaltige Weise herzustellen. Die bekannten Methoden beruhen in erster Linie auf der Palladiumkatalyse, die in der Regel harsche Reaktionsbedingungen und Verzweigungen/Quervernetzungen mit sich bringen. Hier berichten wir über das erste Beispiel einer Ruthenium‐katalysierten C−H Arylierungspolymerisation bei Raumtemperatur, die durch Bestrahlung mit sichtbarem Licht induziert wird. Die vorliegende Polymerisation kann verschiedene meta ‐ und para ‐verknüpfte Polymere in hervorragenden Ausbeuten mit hohen zahlenmittleren molaren Massen herstellen. Das bemerkenswerte Merkmal unserer milden Reaktionsstrategie ist die hohe Chemoselektivität, die zu Polymeren führt, die unter herkömmlichen Reaktionsbedingungen bei hohen Temperaturen nicht zugänglich sind.HORIZON EUROPE European Research Council https://doi.org/10.13039/100019180Deutsche Forschungsgemeinschaft https://doi.org/10.13039/501100001659European Research Council https://doi.org/10.13039/50110000078
Photo‐Induced Ruthenium‐Catalyzed C–H Arylation Polymerization at Ambient Temperature
No full textTransition metal‐catalyzed C–H arylation polymerization (CHAP) is an attractive tool for constructing π‐conjugated polymers in a sustainable manner. However, the existing methods primarily rely on palladium catalysis, which usually entails harsh reaction conditions and branching/cross‐linking. Here we report the first example of an ambient‐temperature ruthenium‐catalyzed C–H arylation polymerization induced by visible light irradiation. The present polymerization can produce various meta‐ and para‐linked polymers in excellent yields with high molecular weights. The remarkable feature of our mild reaction platform is represented by high chemoselectivity, leading to polymers that are otherwise inaccessible under conventional reaction conditions at high temperatures
Rhodaelectro-catalyzed chemo-divergent C–H activations with alkylidenecyclopropanes for selective cyclopropylations
No full textHerein, we report on selectivity control in C–H activations with alkylidenecyclopropanes (ACPs) for the chemo-selective assembly of cyclopropanes or dienes. Thus, unprecedented rhodaelectro-catalyzed C–H activations were realized with diversely decorated ACPs with a wide substrate scope and electricity as the sole oxidant
)–H azidation without directing groups
No full textSelective up-cycling of polyolefins to C(sp 3 )–H azidated materials was achieved by electrocatalysis. The broad scope, ease of scale-up, and late-stage click-diversification are key features.The chemical up-cycling of polymers into value-added materials offers a unique opportunity to place plastic waste in a new value chain towards a circular economy. Herein, we report the selective up-cycling of polystyrenes and polyolefins to C(sp 3 )–H azidated materials under electrocatalytic conditions. The functionalized polymers were obtained with high retention of mass average molecular mass and high functionalization through chemo-selective mangana-electrocatalysis. Our strategy proved to be broadly applicable to a variety of homo- and copolymers. Polyethylene, polypropylene as well as post-consumer polystyrene materials were functionalized by this approach, thereby avoiding the use of hypervalent-iodine reagents in stoichiometric quantities by means of electrocatalysis. This study, hence, represents a chemical oxidant-free polymer functionalization by electro-oxidation. The electrocatalysis proved to be scalable, which highlights its unique feature for a green hydrogen economy by means of the hydrogen evolution reaction (HER).Alexander von Humboldt-Stiftung https://doi.org/10.13039/100005156Deutsche Forschungsgemeinschaft https://doi.org/10.13039/501100001659HORIZON EUROPE European Research Council https://doi.org/10.13039/10001918
Chemodivergent Manganese-Catalyzed C-H Activation: Modular Synthesis of Fluorogenic Probes
No full textPhotoelectrochemical Si–H and Ge–H activation by iron catalysis
No full texthttp://dx.doi.org/10.13039/501100001659 Deutsche Forschungsgemeinschafthttp://dx.doi.org/10.13039/100007215 Verband der Chemischen Industriehttp://dx.doi.org/10.13039/501100004543 China Scholarship Councilhttp://dx.doi.org/10.13039/100010663 European Research Councilhttp://dx.doi.org/10.13039/501100000781 European Research Counci
Chemodivergent Manganese-Catalyzed C-H Activation: Modular Synthesis of Fluorogenic Probes
No full text
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
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