170,564 research outputs found
Remote C–H Functionalizations by Ruthenium Catalysis
No full textAbstract Synthetic transformations of otherwise inert C–H bonds have emerged as a powerful tool for molecular modifications during the last decades, with broad applications towards pharmaceuticals, material sciences, and crop protection. Consistently, a key challenge in C–H activation chemistry is the full control of site-selectivity. In addition to substrate control through steric hindrance or kinetic acidity of C–H bonds, one important approach for the site-selective C–H transformation of arenes is the use of chelation-assistance through directing groups, therefore leading to proximity-induced ortho-C–H metalation. In contrast, more challenging remote C–H activations at the meta- or para-positions continue to be scarce. Within this review, we demonstrate the distinct character of ruthenium catalysis for remote C–H activations until March 2021, highlighting among others late-stage modifications of bio-relevant molecules. Moreover, we discuss important mechanistic insights by experiments and computation, illustrating the key importance of carboxylate-assisted C–H activation with ruthenium(II) complexes. 1 Introduction 2 Stoichiometric Remote C–H Functionalizations 3 meta-C–H Functionalizations 4 para-C–H Functionalizations 5 meta-/ortho-C–H Difunctionalizations 6 Conclusion
Catalogus van de bibliotheken der Maatschappij tot bevordering der toonkunst en der Vereeniging voor Noord-Nederlands muziekgeschiedenis
No full textPreface signed: H. C. Rogge
Arene‐Free Ruthenium(II/IV)‐Catalyzed Bifurcated Arylation for Oxidative C−H/C−H Functionalizations
No full textAbstract Experimental and computational studies provide detailed insight into the selectivity‐ and reactivity‐controlling factors in bifurcated ruthenium‐catalyzed direct C−H arylations and dehydrogenative C−H/C−H functionalizations. Thorough investigations revealed the importance of arene‐ligand‐free complexes for the formation of biscyclometalated intermediates within a ruthenium(II/IV/II) mechanistic manifold.Deutsche Forschungsgemeinschaft https://doi.org/10.13039/50110000165
Metal-catalysed C–Het (F, O, S, N) and C–C bond arylation
No full textThe formation of C–aryl bonds has been the focus of intensive research over the last decades for the construction of complex molecules from simple, readily available feedstocks.The formation of C–aryl bonds has been the focus of intensive research over the last decades for the construction of complex molecules from simple, readily available feedstocks. Traditionally, these strategies involve the coupling of organohalides (I, Br, Cl) with organometallic reagents (Mg, Zn, B, Si, Sn,…) such as Kumada–Corriu, Negishi, Suzuki–Miyaura, Hiyama and Sonogashira cross-couplings. More recently, alternative methods have provided access to these products by reactions with less reactive C–Het (F, O, S, N) and C–C bonds. Compared to traditional methods, the direct cleavage and arylation of these chemical bonds, the essential link in accessible feedstocks, has become increasingly important from the viewpoint of step-economy and functional-group compatibility. This comprehensive review aims to outline the development and advances of this topic, which was organized into (1) C–F bond arylation, (2) C–O bond arylation, (3) C–S bond arylation, (4) C–N bond arylation, and (5) C–C bond arylation. Substantial attention has been paid to the strategies and mechanistic investigations. We hope that this review can trigger chemists to discover more efficient methodologies to access arylation products by cleavage of these C–Het and C–C bonds.The formation of C–aryl bonds has been the focus of intensive research over the last decades for the construction of complex molecules from simple, readily available feedstocks.The formation of C–aryl bonds has been the focus of intensive research over the last decades for the construction of complex molecules from simple, readily available feedstocks. Traditionally, these strategies involve the coupling of organohalides (I, Br, Cl) with organometallic reagents (Mg, Zn, B, Si, Sn,…) such as Kumada–Corriu, Negishi, Suzuki–Miyaura, Hiyama and Sonogashira cross-couplings. More recently, alternative methods have provided access to these products by reactions with less reactive C–Het (F, O, S, N) and C–C bonds. Compared to traditional methods, the direct cleavage and arylation of these chemical bonds, the essential link in accessible feedstocks, has become increasingly important from the viewpoint of step-economy and functional-group compatibility. This comprehensive review aims to outline the development and advances of this topic, which was organized into (1) C–F bond arylation, (2) C–O bond arylation, (3) C–S bond arylation, (4) C–N bond arylation, and (5) C–C bond arylation. Substantial attention has been paid to the strategies and mechanistic investigations. We hope that this review can trigger chemists to discover more efficient methodologies to access arylation products by cleavage of these C–Het and C–C bonds
Metal-catalysed C-Het (F, O, S, N) and C-C bond arylation
No full textThe formation of C-aryl bonds has been the focus of intensive research over the last decades for the construction of complex molecules from simple, readily available feedstocks. Traditionally, these strategies involve the coupling of organohalides (I, Br, Cl) with organometallic reagents (Mg, Zn, B, Si, Sn,...) such as Kumada-Corriu, Negishi, Suzuki-Miyaura, Hiyama and Sonogashira cross-couplings. More recently, alternative methods have provided access to these products by reactions with less reactive C-Het (F, O, S, N) and C-C bonds. Compared to traditional methods, the direct cleavage and arylation of these chemical bonds, the essential link in accessible feedstocks, has become increasingly important from the viewpoint of step-economy and functional-group compatibility. This comprehensive review aims to outline the development and advances of this topic, which was organized into (1) C-F bond arylation, (2) C-O bond arylation, (3) C-S bond arylation, (4) C-N bond arylation, and (5) C-C bond arylation. Substantial attention has been paid to the strategies and mechanistic investigations. We hope that this review can trigger chemists to discover more efficient methodologies to access arylation products by cleavage of these C-Het and C-C bonds
Distal Weak Coordination of Acetamides in Ruthenium(II)‐Catalyzed C−H Activation Processes
No full textAbstract C−H activations with challenging arylacetamides were accomplished by versatile ruthenium(II) biscarboxylate catalysis. The distal C−H functionalization offers ample scope—including twofold oxidative C−H functionalizations and alkyne hydroarylations—through facile base‐assisted internal electrophilic‐type substitution (BIES) C−H ruthenation by weak O ‐coordination
Consumer Information in the food service industry vs. food retailing
No full textIn order to define consumer expectations over a traceability and information system for the entire food supply chain, the information behaviour of consumers in the food service industry has been subject to an analysis for the first time. In comparison to consumers in retailing, significant differences appear in information seeking behaviour as well as in the information desired.meat traceability, consumer behaviour, food service industry, Consumer/Household Economics,
- …
