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Articles de revues sur le sujet "C-c bond forming processes"
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Martín, Cristina del Mar García, José Ignacio Hernández García, Sebastián Bonardd et David Díaz Díaz. « Lignin-Based Catalysts for C–C Bond-Forming Reactions ». Molecules 28, no 8 (16 avril 2023) : 3513. http://dx.doi.org/10.3390/molecules28083513.
Texte intégralRésumé :
Carbon–carbon (C–C) bond formation is the key reaction in organic synthesis to construct the carbon framework of organic molecules. The continuous shift of science and technology toward eco-friendly and sustainable resources and processes has stimulated the development of catalytic processes for C–C bond formation based on the use of renewable resources. In this context, and among other biopolymer-based materials, lignin has attracted scientific attention in the field of catalysis during the last decade, either through its acid form or as a support for metal ions and metal nanoparticles that drive the catalytic activity. Its heterogeneous nature, as well as its facile preparation and low cost, provide competitive advantages over other homogeneous catalysts. In this review, we have summarized a variety of C–C formation reactions, such as condensations, Michael additions of indoles, and Pd-mediated cross-coupling reactions that were successfully carried out in the presence of lignin-based catalysts. These examples also involve the successful recovery and reuse of the catalyst after the reaction.
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Valdés, Carlos, Raquel Barroso et María Cabal. « Pd-catalyzed Auto-Tandem Cascades Based on N-Sulfonylhydrazones : Hetero- and Carbocyclization Processes ». Synthesis 28, no 19 (10 août 2017) : 4434–47. http://dx.doi.org/10.1055/s-0036-1588535.
Texte intégralRésumé :
The Pd-catalyzed cross-coupling between N-tosylhydrazones and organic halides is a powerful method for the creation of C–C bonds. This transformation has been included recently in cascade processes in which the same catalyst promotes various independent catalytic steps, a process known as auto-tandem catalysis. This strategy proves to be very useful for the construction of relatively complex carbo- and heterocyclic structures, as well as for the generation of molecular diversity. This short review will cover the different Pd-catalyzed auto-tandem reactions involving N-tosylhydrazones organized by the bond-forming sequence: C–C/C–N and C–C/C–C. Some examples of related tandem reactions leading to acyclic compounds are also highlighted.1 Introduction2 Auto-Tandem C–C/C–N Bond-Forming Reactions3 Auto-Tandem C–C/C–C Bond-Forming Reactions4 Tandem Reactions for the Synthesis of Linear Molecules5 Summary and Outlook
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Liu, Jialin, Xiaoyu Xiong, Jie Chen, Yuntao Wang, Ranran Zhu et Jianhui Huang. « Double C–H Activation for the C–C bond Formation Reactions ». Current Organic Synthesis 15, no 7 (16 octobre 2018) : 882–903. http://dx.doi.org/10.2174/1570179415666180720111422.
Texte intégralRésumé :
Background: Among the numerous bond-forming patterns, C–C bond formation is one of the most useful tools for building molecules for the chemical industry as well as life sciences. Recently, one of the most challenging topics is the study of the direct coupling reactions via multiple C–H bond cleavage/activation processes. A number of excellent reviews on modern C–H direct functionalization have been reported by Bergman, Bercaw, Yu and others in recent years. Among the large number of available methodologies, Pdcatalyzed reactions and hypervalent iodine reagent mediated reactions represent the most popular metal and non-metal involved transformations. However, the comprehensive summary of the comparison of metal and non-metal mediated transformations is still not available. Objective: The review focuses on comparing these two types of reactions (Pd-catalyzed reactions and hypervalent iodine reagent mediated reactions) based on the ways of forming new C–C bonds, as well as the scope and limitations on the demonstration of their synthetic applications. Conclusion: Comparing the Pd-catalyzed strategies and hypervalent iodine reagent mediated methodologies for the direct C–C bond formation from activation of C-H bonds, we clearly noticed that both strategies are powerful tools for directly obtaining the corresponding pruducts. On one hand, the hypervalent iodine reagents mediated reactions are normally under mild conditions and give the molecular diversity without the presence of transition-metal, while the Pd-catalyzed approaches have a broader scope for the wide synthetic applications. On the other hand, unlike Pd-catalyzed C-C bond formation reactions, the study towards hypervalent iodine reagent mediated methodology mainly focused on the stoichiometric amount of hypervalent iodine reagent, while few catalytic reactions have been reported. Meanwhile, hypervalent iodine strategy has been proved to be more efficient in intramolecular medium-ring construction, while there are less successful examples on C(sp3)–C(sp3) bond formation. In summary, we have demonstrated a number of selected approaches for the formation of a new C–C bond under the utilization of Pd-catalyzed reaction conditions or hyperiodine reagents. The direct activations of sp2 or sp3 hybridized C–H bonds are believed to be important strategies for the future molecular design as well as useful chemical entity synthesis.
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Todd, David P., Benjamin B. Thompson, Alex J. Nett et John Montgomery. « Deoxygenative C–C Bond-Forming Processes via a Net Four-Electron Reductive Coupling ». Journal of the American Chemical Society 137, no 40 (5 octobre 2015) : 12788–91. http://dx.doi.org/10.1021/jacs.5b08448.
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Correa, Arkaitz, et Marcos Segundo. « Cross-Dehydrogenative Coupling Reactions for the Functionalization of α-Amino Acid Derivatives and Peptides ». Synthesis 50, no 15 (25 juin 2018) : 2853–66. http://dx.doi.org/10.1055/s-0037-1610073.
Texte intégralRésumé :
The functionalization of typically unreactive C(sp3)–H bonds holds great promise for reducing the reliance on existing functional groups while improving atom-economy and energy efficiency. As a result, this topic is a matter of genuine concern for scientists in order to achieve greener chemical processes. The site-specific modification of α-amino acid and peptides based upon C(sp3)–H functionalization still represents a great challenge of utmost synthetic importance. This short review summarizes the most recent advances in ‘Cross-Dehydrogenative Couplings’ of α-amino carbonyl compounds and peptide derivatives with a variety of nucleophilic coupling partners.1 Introduction2 C–C Bond-Forming Oxidative Couplings2.1 Reaction with Alkynes2.2 Reaction with Alkenes2.3 Reaction with (Hetero)arenes2.4 Reaction with Alkyl Reagents3 C–Heteroatom Bond-Forming Oxidative Couplings3.1 C–P Bond Formation3.2 C–N Bond Formation3.3 C–O and C–S Bond Formation4 Conclusions
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Daoust, Benoit, Nicolas Gilbert, Paméla Casault, François Ladouceur et Simon Ricard. « 1,2-Dihaloalkenes in Metal-Catalyzed Reactions ». Synthesis 50, no 16 (9 juillet 2018) : 3087–113. http://dx.doi.org/10.1055/s-0037-1610174.
Texte intégralRésumé :
1,2-Dihaloalkenes readily undergo simultaneous or sequential difunctionalization through transition-metal-catalyzed reactions, which makes them attractive building blocks for complex unsaturated motifs. This review summarizes recent applications of such transformations in C–C and C–heteroatom bond forming processes. The facile synthesis of stereodefined alkene derivatives, as well as aromatic and heteroatomic compounds, from 1,2-dihaloalkenes is thus outlined.1 Introduction2 Synthesis of 1,2-Dihaloalkenes3 C–C Bond Forming Reactions4 C–Heteroatom Bond Forming Reactions5 Conclusion
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Todd, David P., Benjamin B. Thompson, Alex J. Nett et John Montgomery. « ChemInform Abstract : Deoxygenative C-C Bond-Forming Processes via a Net Four-Electron Reductive Coupling. » ChemInform 47, no 12 (mars 2016) : no. http://dx.doi.org/10.1002/chin.201612061.
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Buzzetti, Luca, Alexis Prieto, Sudipta Raha Roy et Paolo Melchiorre. « Radical-Based C−C Bond-Forming Processes Enabled by the Photoexcitation of 4-Alkyl-1,4-dihydropyridines ». Angewandte Chemie 129, no 47 (24 octobre 2017) : 15235–39. http://dx.doi.org/10.1002/ange.201709571.
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Buzzetti, Luca, Alexis Prieto, Sudipta Raha Roy et Paolo Melchiorre. « Radical-Based C−C Bond-Forming Processes Enabled by the Photoexcitation of 4-Alkyl-1,4-dihydropyridines ». Angewandte Chemie International Edition 56, no 47 (24 octobre 2017) : 15039–43. http://dx.doi.org/10.1002/anie.201709571.
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Buchspies, Jonathan, Md Mahbubur Rahman et Michal Szostak. « Transamidation of Amides and Amidation of Esters by Selective N–C(O)/O–C(O) Cleavage Mediated by Air- and Moisture-Stable Half-Sandwich Nickel(II)–NHC Complexes ». Molecules 26, no 1 (2 janvier 2021) : 188. http://dx.doi.org/10.3390/molecules26010188.
Texte intégralRésumé :
The formation of amide bonds represents one of the most fundamental processes in organic synthesis. Transition-metal-catalyzed activation of acyclic twisted amides has emerged as an increasingly powerful platform in synthesis. Herein, we report the transamidation of N-activated twisted amides by selective N–C(O) cleavage mediated by air- and moisture-stable half-sandwich Ni(II)–NHC (NHC = N-heterocyclic carbenes) complexes. We demonstrate that the readily available cyclopentadienyl complex, [CpNi(IPr)Cl] (IPr = 1,3-bis(2,6-diisopropylphenyl)imidazol-2-ylidene), promotes highly selective transamidation of the N–C(O) bond in twisted N-Boc amides with non-nucleophilic anilines. The reaction provides access to secondary anilides via the non-conventional amide bond-forming pathway. Furthermore, the amidation of activated phenolic and unactivated methyl esters mediated by [CpNi(IPr)Cl] is reported. This study sets the stage for the broad utilization of well-defined, air- and moisture-stable Ni(II)–NHC complexes in catalytic amide bond-forming protocols by unconventional C(acyl)–N and C(acyl)–O bond cleavage reactions.
Thèses sur le sujet "C-c bond forming processes"
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Das, Sajal. « Investigations on synthetic organic transformations : application to C-C and C-N bond forming processes ». Thesis, University of North Bengal, 2007. http://hdl.handle.net/123456789/1146.
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Reeds, Jonathan P. « Exploiting imidate ligand effects in transition metal-mediated C-C bond forming processes ». Thesis, University of York, 2010. http://etheses.whiterose.ac.uk/1240/.
Texte intégralRésumé :
The effects of substituting (pseudo)halide for imidate ligands in Au(I) and Au(III) ([AuBr(NHC)] and [AuBr3(NHC)]), Ru(II) ([RuCl2(CHR)(L2)]) and Pd(II) ([Pd(OAc)2]) complexes has been investigated. The activity of these complexes as (pre)catalysts in enyne cycloisomerisation and propargylic nucleophilic substitution, diene ring-closing metathesis and ring-opening metathesis polymerisation and direct arylation reactions, respectively, has been determined. [Au(N-imidate)(NHC)] and [AuBr2(N-imidate)(NHC)] complexes were prepared and the structure and bonding of the complexes examined spectroscopically and crystallographically. The [AuBr2(N-imidate)(NHC)] complexes, in combination with co-catalytic silver salts, were tested for activity in the cycloisomerisation of 1,5- and 1,6- enynes and found to be more effective than tribromide analogues. Kinetic analysis of the reactions showed subtle changes to the imidate structure had a pronounced effect on the activity of the complexes and the use of the silver salt Ag[Al(OC(CF3)3)4] as a co-catalyst greatly increased catalytic activity. The complexes were also found to catalyse a unique tandem nucleophilic substitution-cycloisomerisation of propargyl alcohols and allylsilanes. [AuBr2(N-tfs)(ItPe)] was found to be an effective precatalyst for this reaction whilst Au(III) tribromide and Au(I) complexes were ineffective. 1,3-Diarylbicyclo[3.1.0]hexenes products were found to undergo a post-reaction ambient temperature 1,3-carbon shift isomerisation. The complex [Ru(N-tfs)2(o-iPrO-CHPh)(IMesH2)] was prepared and characterised spectroscopically and crystallographically. The complex was found to be inactive in the ring-closing metathesis and ring-opening metathesis polymerisation of alkenes. Attempts to selectively substitute chloride for imidate ligands derived from imides with higher pKa’s of 8.3-9.7 (in water) resulted in decomposition of the alkylidene or benzylidene ligand. [Pd(imidate)2(MeCN)] and [Pd(imidate)2(THT)] complexes were prepared and analysed by NMR and infra-red spectroscopy. The complexes were tested for activity in the direct arylation of imidazole with iodoarenes without added base or neutral ligands. The activity of the complexes was to some degree dependant on the structure of the imidate ligand, possessing moderate activity in comparison with [Pd(OAc)2]. The activity of other palladium sources and conditions for this reaction were investigated and it was found that the formation of Pd nanoparticles may be key to reaction progression.
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Yang, Yang Ph D. Massachusetts Institute of Technology. « New reactivity and selectivity in transition metal-catalyzed C-C and C-N bond forming processes ». Thesis, Massachusetts Institute of Technology, 2015. http://hdl.handle.net/1721.1/101558.
Texte intégralRésumé :
Thesis: Ph. D. in Organic Chemistry, Massachusetts Institute of Technology, Department of Chemistry, 2015.Cataloged from PDF version of thesis. Volume 1 (page 1 to page 510) ; Volume 2 (page 511 to 881). Duplicated pages for pages 195 to 240 are bound after page 881.
Includes bibliographical references.
Part I. Palladium-Catalyzed Carbon-Carbon Bond Forming Cross-Couplings Chapter 1. Ligand-Controlled Palladium-Catalyzed Regiodivergent Suzuki-Miyaura Cross-Coupling of Allylboronates and Aryl Halides An orthogonal set of catalyst systems based on the use of two biarylphosphine ligands has been developed for the Suzuki-Miyaura coupling of 3,3-disubstituted and 3-monosubstituted allylboronates with (hetero)aryl halides. These methods allow for the regiodivergent preparation of either the ct- or the [gamma]-isomeric coupling product with high levels of site selectivity using a common allylboron building block. Preliminary investigations have demonstrated the feasibility of an enantioselective variant for the [gamma]-selective cross-coupling using chiral monodentate biarylphosphine ligands. Chapter 2. Palladium-Catalyzed Completely Linear-Selective Negishi Coupling of 3,3-Disubstituted Organozinc Reagents with Aryl and Vinyl Electrophiles A palladium-catalyzed general and completely linear-selective Negishi coupling of 3,3- disubstituted allyl organozinc reagents with (hetero)aryl and vinyl electrophiles has been developed. This method provided an effective means for accessing highly functionalized aromatic and heteroaromatic compounds bearing prenyl-type side chains. The utility of the current protocol was further illustrated in the concise synthesis of the anti-HIV natural product siamenol. Chapter 3. Palladium-Catalyzed Highly Selective Negishi Cross-Coupling of Secondary Alkylzinc Reagents with Aryl and Heteroaryl Halides The palladium-catalyzed Negishi cross-coupling of secondary alkylzinc reagents and heteroaryl halides with high levels of regioisomeric retention has been described. The development of a series of biarylphosphine ligands has led to the identification of an improved catalyst for the coupling of electron-deficient heterocyclic substrates. Preparation and characterization of oxidative addition complex (L)Pd(Ar)(Br) provided insight into the unique reactivity of palladium catalysts based on CPhos-type biarylphosphine ligands in facilitating challenging reductive elimination processes. Chapter 4. Mechanistic Studies on the Aryl-Trifluoromethyl Reductive Elimination from Pd(II) Complexes Based on Biarylphosphine Ligands A series of monoligated (L)Pd(Ar)(CF₃) (L = dialkyl biarylphosphine) have been prepared and studied in an effort to shed light on the mechanism of the aryl-trifluoromethyl reductive elimination from these systems. Combined experimental and computational investigations revealed unique reactivity and binding modes of (L)Pd(Ar)(CF₃) complexes derived from BrettPhos-type biarylphosphines. In contrast to a variety of C-C and C-heteroatom bond forming reductive eliminations, kinetic measurements showed this Ar-CF₃ reductive elimination is largely insensitive to the electronic nature of the to-be-eliminated aryl substituent. Furthermore, the aryl group serves as the nucleophilic coupling partner in this reductive elimination process. The structure-reactivity relationship of biarylphosphine ligands was also investigated, uncovering distinct roles of the ipso-arene and alkoxy interactions in affecting these reductive elimination reactions. Part II. Copper-Catalyzed Carbon-Carbon and Carbon-Nitrogen Bond Formation via Olefin Functionalization Chapter 5. Copper-Catalyzed ortho C-H Cyanation of Vinylarenes A copper-catalyzed regioselective ortho C-H cyanation of vinylarenes has been developed. This method provides an effective means for the selective functionalization of vinylarene derivatives. A copper-catalyzed cyanative dearomatization mechanism is proposed to account for the regiochemical course of this reaction. This mechanism has been validated through density functional theory calculations. Computational studies revealed that the high level of ortho selectivity in the electrophilic cyanation event originates from a unique six-membered transition state that minimizes unfavorable steric repulsions. Chapter 6. Regio- and Stereospecific 1,3-Allyl Group Transfer Triggered by a Copper-Catalyzed Borylation/ortho-Cyanation Cascade A copper-catalyzed borylation/cyanation/allyl group transfer cascade has been developed. This process features an unconventional copper-catalyzed electrophilic dearomatization followed by the subsequent regio- and stereospecific 1,3-transposition of the allyl fragment enabled by the aromatization-driven Cope rearrangement. This method provides an effective means for the construction of adjacent tertiary and quaternary stereocenters with high levels of stereochemical purity. Chapter 7. Copper-Catalyzed Asymmetric Hydroamination of Unactivated Internal Olefins: an Effective Means to Access Highly Enantioenriched Aliphatic Amines Catalytic assembly of enantiopure aliphatic amines from abundant and readily available precursors has long been recognized as a paramount challenge in synthetic chemistry. We describe a mild and general copper-catalyzed hydroamination that effectively converts unactivated internal olefins-an important yet unexploited class of abundant feedstock chemicals-into highly enantioenriched [alpha]-branched amines (>/= 96% ee) featuring two minimally differentiated aliphatic substituents. This method provides a powerful means to access a broad range of advanced, highly functionalized enantioenriched amines of interest in pharmaceutical research and other areas.
by Yang Yang.
Ph. D. in Organic Chemistry
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Perry, Ian B. (Ian Brooks). « Transition metal-facilitated C-C and C-F bond forming ». Thesis, Massachusetts Institute of Technology, 2017. http://hdl.handle.net/1721.1/112449.
Texte intégralRésumé :
Thesis: S.B., Massachusetts Institute of Technology, Department of Chemistry, 2017.Cataloged from PDF version of thesis. "June 2017."
Includes bibliographical references.
Chapter 1. Copper-Catalyzed Asymmetric Addition of Olefin-Derived Nucleophiles to Ketones A copper (I) catalyzed coupling olefins and ketones has been developed for the diastereo- and enantioselective generation of homopropargyl alcohols bearing vicinal stereocenters. This method allows for the generation of enantioenriched tertiary alcohols with a high degree of functional group compatibility. The utility of the process is further illustrated by a large scale synthesis with extremely low catalyst loading as well as the late stage modification of several pharmaceuticals. Chapter 2. Copper-Catalyzed Enantioselective Addition of Styrene-Derived Nucleophiles to Imines We describe the catalytic generation of amines bearing vicinal stereocenters with a moderate degree of diastereoselectivity. The stereoselective hydrocupration of an unactivated olefinic component is followed by nucleophilic addition of the organocuprate to an N-phosphinoyl protected imine. The mild and general process tolerates a broad-range of functionality, and the process was shown to be successful at a gram-scale synthesis. Chapter 3. Palladium-facilitated Regioselective Nucleophilic Fluorination of Aryl and Heteroaryl Halides. The preliminary findings regarding an aryl and heteroaryl halide fluorination process facilitated by palladium as a reagent is described. Stoichiometric studies illustrate the utility of the method in producing aryl fluorides with unprecedented regioselectivity, and preliminary studies into the fluorination of five- and six-membered heteroaryl bromides are described. Halogen atom substitution as a route to irreversible oxidative addition of aryl and heteroaryl halides is discussed. This strategy may serve to facilitate the fluorination of particularly problematic heteroaryl bromide and chloride substrates.
by Ian B. Perry.
S.B.
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Mudarra, Alonso Ángel Luis. « Coinage complexes in C-C and C-N bond-forming reactions ». Doctoral thesis, Universitat Rovira i Virgili, 2020. http://hdl.handle.net/10803/670357.
Texte intégralRésumé :
Els complexos organometàl·lics de coure, plata i or juguen un paper fonamental com espècies reactives
en diverses transformacions químiques. Aquesta tesi aporta coneixement sobre el comportament
d’aquests complexos en la formació d’enllaços C-C i/o C-N. En concret, estudiem: i) el mecanisme de
reacció a través del qual els complexos de coure co-catalitzen un acoblament oxidant en el context de
sistemes bimetàl·lics de rodi i coure; ii) el potencial de nucleòfils de plata com a agents transmetal·lants
en reaccions de trifluorometilació catalitzades per pal·ladi; iii) el mecanisme de reacció de sistemes
bimetàl·lics de Pd/Ag emprant un sistema model; i iv) el comportament de complexos bis(trifluorometil)
cuprat, argentat i aurat com a nucleòfils. En aquesta tesi, on s´han combinat estudis experimentals i
computacionals, s’ha adquirit nou coneixement sobre els processos estudiats, i s’ha contribuït al camp de
la recerca química basada en el coneixement.Los complejos organometálicos de cobre, plata y oro juegan un papel fundamental como especies reactivas en diversas transformaciones químicas. Esta tesis aporta conocimiento sobre el comportamiento de estos complejos en la formación de enlaces C-C y/o C-N. En concreto, estudiamos: i) el mecanismo de reacción por el cual complejos de cobre co-catalizan un acoplamiento oxidante en el contexto de sistemas bimetálicos de rodio y cobre; ii) el potencial de nucleófilos de plata como agentes transmetalantes en reacciones de trifluorometilación catalizadas por paladio; iii) el mecanismo de reacción de sistemas bimetálicos de Pd/Ag usando un sistema modelo; y iv) el comportamiento de complejos bis(trifluorometil) cuprato, argentato y aurato como nucleófilos. En esta tesis, donde se han combinado estudios experimentales y computacionales, se ha adquirido nuevo conocimiento sobre los procesos estudiados, y se ha contribuido al campo de la investigación química basada en el conocimiento.
Organometallic coinage metal complexes are be key reactive species for promoting a wide variety of chemical transformations. This thesis improves the understanding the behavior of these complexes in relevant C-C and/or C-N bond-forming reactions. Specifically, we have explored: i) the mechanistic intricacies of copper species as co-catalyst in the context of rhodium/copper-catalyzed oxidative coupling reactions; ii) the capability of silver nucleophiles as transmetalating agents in palladium-catalyzed trifluoromethylation reactions; iii) the reaction mechanism of Pd/Ag bimetallic reactions using a model system as probe; and, iv) the study of bis(trifluoromethyl) coinage metallates as nucleophiles. The fundamental insights gathered in this Thesis, encompassing both experimental and computational approaches, improve our understanding of the processes under study and make a contribution to the general field of knowledge-driven research in Chemistry.
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Kanuru, Vijaykumar. « Understanding surface mediated C-C and C-N bond forming reactions ». Thesis, University of Cambridge, 2010. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.608956.
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Pilarski, Lukasz T. « Palladacycles for non-redox C-C bond forming reactions ». Thesis, University of Bristol, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.495644.
Texte intégralRésumé :
This thesis is concerned with the use of palladacyclic complexes as catalysts for C-C and C-heteroatom bond-forming reactions in which an oxidation state change of the metal centre is not part of the catalytic cycle. To this end, the investigation of a range of known K²-C,L-based palladacycles in the allylation of aldehyde and imine substrates using stannanes, as well as the 1,4-conjugate arylation of enones and imines using arylboronic acids under mild conditions is described. In each case the commercially available phosphite-based dimeric palladacycle is found to be the most active complex capable of achieving excellent conversions (>90%) at the 0.5 - 2.5mol% loading range. Three previously unknown phosphinite and amidophosphinite palladium pincer complexes are also synthesised, characterised (including crystallographically) and tested in the 1,4-conjugate addition of phenylboronic acid to chalcone and found to be inactive.
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Lomas, Sarah. « C-C bond forming catalysis with alkaline earth acetylides ». Thesis, University of Bath, 2013. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.604644.
Texte intégralRésumé :
After spending so many years in the shadow of magnesium chemistry the chemical abilities of the heavier alkaline earth metals, calcium, strontium and barium are beginning to emerge. This thesis is concerned with the development of a catalytic reactivity for the heavier alkaline earth metals. By taking inspiration from lanthanide metal catalysis, this thesis will begin by describing the hydroamination and hydrophosphination of unsaturated molecules catalysed by lanthanide and group 2 metals before extending this work to the group 2 catalysed hydroacetylation of terminal acetylenes (chapter 2), and the insertion of unsaturated bonds of carbodiimides (chapter 4), and organic isocyanates (chapter 5) into the polarised M-C bonds of group 2 acetylides. The third chapter of this thesis will describe the observation of the first acetylide coupling with a group 2 metal complex and extension of this reactivity to a catalytic process.
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Varma, Sreejith Jayasree. « Mimicking C-C bond forming reactions of core metabolism ». Thesis, Strasbourg, 2018. http://www.theses.fr/2018STRAF038/document.
Texte intégralRésumé :
Toutes les formes de vie assemblent et désassemblent continuellement des composés chimiques via un processus de consommation d'énergie appelé métabolisme. Le métabolisme est généralement modélisé en chimie et biologie par un cycle. Ce modèle dynamique traduit la transformation de composés de base en une cascade de produits appelés métabolites. Celui-ci est comparable à un ouragan à l’échelle moléculaire. De manière analogique et imagée un cyclone est constitué de deux éléments, l'air et l'eau, et transforme l’environnement qui l’entoure par un processus endothermique (consommateur d’énergie). Traditionnellement, la recherche chimique sur les origines de la vie est concentrée principalement sur la synthèse de composés chimiques sans suffisamment apprécier leur place dans la plus grande organisation biochimique de la vie. La vie construit toutes ses molécules à partir du dioxyde de carbone, pourtant elle manque étonnamment d'innovation à cet égard. Malgré presque 4 milliards d'années d'évolution, les organismes autotrophes utilisent seulement six voies différentes pour construire leurs molécules à partir du CO2. Parmi elles, deux voies – la voie de l’acétyle CoA (aussi appelée voie Wood-Ljungdahl) et le cycle du rTCA (également appelé le cycle de Krebs inverse) - sont considérées comme primitives, et contiennent les cinq molécules servant de précurseurs chimiques universels pour toute la biochimie. Comment et pourquoi les voies de l’acétyle CoA et du rTCA sont-elles apparues? Pour répondre à cette question, une recherche systématique a été effectuée afin de trouver des catalyseurs chimiques non-enzymatiques ou des minéraux simples, ainsi que des réactifs pouvant promouvoir les réactions d'anabolisme principal, particulièrement la voie de l’Acétyle CoA et le cycle de rTCA. A l’origine, pour créer les molécules organiques complexes comme les enzymes il a fallu que des molécules plus simples avec un moins grand nombre de carbone se forme sur terre et cela à partir du CO2. On peut donc supposer que les premiers produits à plusieurs carbones sont issus de synthèse totalement inorganique comme celles développer dans notre laboratoire, plutôt que d’une évolution chimique et organométallique simultanée, c’est-à-dire une interaction efficace entre une molécule carbonée et un ou plusieurs métaux à l’instar de certains enzymes. Après avoir trouvé autant de façons possible de promouvoir individuellement chaque étapes des cycles catalytiques étudiés, seules les conditions réactionnelles mutuellement compatibles (à savoir des conditions permettant de produire l’ensemble des métabolites dans le bon ordre) ont été retenuAll life forms continuously build up and break down its constituent chemical building blocks, through an energy consuming process called metabolism. Just like a hurricane’s dynamic patterns and its building blocks (air and water) as being equally fundamental to its nature, so too should metabolism’s dynamic chemical patterns and chemical building blocks be viewed as equally characteristic. Traditionally, much chemical research on the origins of life is overly focused on the synthesis of chemical building blocks without sufficiently appreciating their place in life’s larger biochemical self-organization. Life ultimately builds all of its molecules from carbon dioxide, yet it is surprisingly lacking in innovation in this respect. Despite nearly 4 billion years of evolution, autotrophic organisms use only six pathways to build their molecules from CO2. Two of these pathways – the acetyl CoA pathway (also known as the Wood-Ljungdahl pathway) and rTCA cycle (also known as the reverse Krebs cycle) - are thought to be ancestral, with just five molecules within them serving as the universal chemical precursors for all of biochemistry. How and why did these pathways get their start? To answer this question, a systematic search was designed to find simple, non-enzymatic chemical or mineral catalysts and reagents, that can promote the reactions of core anabolism, particularly the acetyl CoA pathway and the rTCA cycle. After finding as many ways as possible to promote each reaction, they could be narrowed down to mutually compatible conditions where many reactions can occur in sequence. The more of core anabolism that can be achieved under a single set of purely chemical conditions, the more likely it is to have constituted early prebiotic chemistry rather than a later product of chemical and biological evolution
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Wolfe, John P. (John Perry) 1970. « Late transition metal catalyzed C-N and C-C bond forming reactions ». Thesis, Massachusetts Institute of Technology, 1999. http://hdl.handle.net/1721.1/9521.
Texte intégralRésumé :
Thesis (Ph.D.)--Massachusetts Institute of Technology, Dept. of Chemistry, 1999.Includes bibliographical references.
New methods for the palladium-catalyzed amination of aryl halides are described. Key to these is the development of new catalysts and reaction conditions for these transformations. Initially, P(o-tol)3 ligated palladium catalysts were investigated but gave way to systems that used chelating phosphine ligands which substantially expanded the scope of the catalytic amination methodology. Palladium catalyst systems based on BINAP ((2,2'-diphenylphosphino)-1, 1 '-binaphthyl) allowed for the transformation of a much wider range of amines and aryl halide substrates, as well as aryl triflates. Of practical significance was that the use of cesium carbonate as a base at 100 °C substantially increased the functional group tolerance of the method. Palladium catalysts supported by novel, bulky, electron-rich phosphine ligands are exceptionally effective in the C-N, C-0, and C-C coupling procedures. For some substrate combinations, these palladium catalysts are effective for the room-temperature catalytic amination of aryl chlorides. These palladium catalysts are also highly effective for Suzuki coupling reactions of aryl bromides and chlorides at room temperature. Suzuki coupling reactions of aryl bromides and aryl chlorides are effective at very low catalyst loadings (0.000001-0.005 mol % Pd for ArBr, 0.02-0.05 mol % for ArCI) at 100 °C, and reactions of hindered aryl halides or boronic acids are effected at moderate catalyst loadings (1 mol % Pd). The high reactivity of these catalysts towards aryl chlorides challenges the conventional dogma that chloride substrates cannot be transformed under mild conditions with palladium catalysts, and significantly expands the pool of substrates available for cross-coupling chemistry.
by John P. Wolfe.
Ph.D.
Livres sur le sujet "C-c bond forming processes"
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Mahrwald, Rainer. Enantioselective Organocatalyzed Reactions II : Asymmetric C-C Bond Formation Processes. Dordrecht : Springer Science+Business Media B.V., 2011.
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Mahrwald, Rainer. Enantioselective Organocatalyzed Reactions II : Asymmetric C-C Bond Formation Processes. Springer, 2013.
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Mahrwald, Rainer. Enantioselective Organocatalyzed Reactions II : Asymmetric C-C Bond Formation Processes. Springer, 2016.
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ARSHAD, NUZHAT. C-P and C-C Bond Forming Reactions Based on Carbostyrils and Thioamide : Phosphine Ligands and Thioamide Derivatives. VDM Verlag Dr. Müller, 2010.
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Andersson, Pher G. Innovative Catalysis in Organic Synthesis : Oxidation, Hydrogenation, and C-X Bond Forming Reactions. Wiley & Sons, Incorporated, John, 2012.
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Andersson, Pher G. Innovative Catalysis in Organic Synthesis : Oxidation, Hydrogenation, and C-X Bond Forming Reactions. Wiley & Sons, Incorporated, John, 2012.
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Andersson, Pher G. Innovative Catalysis in Organic Synthesis : Oxidation, Hydrogenation, and C-X Bond Forming Reactions. Wiley & Sons, Limited, John, 2012.
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Andersson, Pher G. Innovative Catalysis in Organic Synthesis : Oxidation, Hydrogenation, and C-X Bond Forming Reactions. Wiley & Sons, Incorporated, John, 2012.
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Anjum, Rani Lill, et Stephen Mumford. Mutual Manifestation and Martin’s Two Triangles. Oxford University Press, 2017. http://dx.doi.org/10.1093/oso/9780198796572.003.0006.
Texte intégralRésumé :
When and how do powers manifest themselves? There are two models. The orthodox view has powers standing in need of stimuli, which once received issue in responses. This model portrays powers as passive. The stimuli are powerful, but the powers are disempowered, turning the order of explanation on its head. The second model is more promising: C. B. Martin’s notion of mutual manifestation partnering. Powers exercise when they meet their reciprocal partners and produce something jointly that they could not have produced alone. In his chapter on causation, Martin offers an analogy to explain mutual manifestation: it is like two triangular cards coming together to form a square. The triangles do not cause the square; they become the square. We argue that although mutual manifestation is the right model, Martin’s analogy of the two triangles is misleading. If we look at natural processes in which powers exercise and manifest themselves, we see that three revisions are needed to the analogy. First, the triangles need not become the square immediately. It can take time for a process to unfold. Second, powers compose often in a non-linear fashion. This would mean that the area of the square need not be the sum of the areas of the two triangles. Third, component powers needn’t be found in their resultant powers. This would be like the two triangles sometimes forming a circle rather than a square. Martin’s analogy depicted mereological composition rather than the natural processes issuing from powers and, contrary to his claim, causation is indeed the notion we should be thinking of.
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Trieloff, Mario. Noble Gases. Oxford University Press, 2017. http://dx.doi.org/10.1093/acrefore/9780190647926.013.30.
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This is an advance summary of a forthcoming article in the Oxford Encyclopedia of Planetary Science. Please check back later for the full article.Although the second most abundant element in the cosmos is helium, noble gases are also called rare gases. The reason is that they are not abundant on terrestrial planets like our Earth, which is characterized by orders of magnitude depletion of—particularly light—noble gases when compared to the cosmic element abundance pattern. Indeed, such geochemical depletion and enrichment processes make noble gases so versatile concerning planetary formation and evolution: When our solar system formed, the first small grains started to adsorb small amounts of noble gases from the protosolar nebula, resulting in depletion of light He and Ne when compared to heavy noble gases Ar, Kr, and Xe: the so-called planetary type abundance pattern. Subsequent flash heating of the first small mm to cm-sized objects (chondrules and calcium, aluminum rich inclusions) resulted in further depletion, as well as heating—and occasionally differentiation—on small planetesimals, which were precursors of larger planets and which we still find in the asteroid belt today from where we get rocky fragments in form of meteorites. In most primitive meteorites, we even can find tiny rare grains that are older than our solar system and condensed billions of years ago in circumstellar atmospheres of, for example, red giant stars. These grains are characterized by nucleosynthetic anomalies and particularly identified by noble gases, for example, so-called s-process xenon.While planetesimals acquired a depleted noble gas component strongly fractionated in favor of heavy noble gases, the sun and also gas giants like Jupiter attracted a much larger amount of gas from the protosolar nebula by gravitational capture. This resulted in a cosmic or “solar type” abundance pattern, containing the full complement of light noble gases. Contrary to Jupiter or the sun, terrestrial planets accreted from planetesimals with only minor contributions from the protosolar nebula, which explains their high degree of depletion and basically “planetary” elemental abundance pattern. Indeed this depletion enables another tool to be applied in noble gas geo- and cosmochemistry: ingrowth of radiogenic nuclides. Due to heavy depletion of primordial nuclides like 36Ar and 130Xe, radiogenic ingrowth of 40Ar by 40K decay, 129Xe by 129I decay, or fission Xe from 238U or 244Pu decay are precisely measurable, and allow insight in the chronology of fractionation of lithophile parent nuclides and atmophile noble gas daughters, mainly caused by mantle degassing and formation of the atmosphere.Already the dominance of 40Ar in the terrestrial atmosphere allowed C. F v. Weizsäcker to conclude that most of the terrestrial atmosphere originated by degassing of the solid Earth, which is an ongoing process today at mid ocean ridges, where primordial helium leaves the lithosphere for the first time. Mantle degassing was much more massive in the past; in fact, most of the terrestrial atmosphere formed during the first 100 million years of Earth´s history, and was completed at about the same time when the terrestrial core formed and accretion was terminated by a giant impact that also formed our moon. However, before that time, somehow also tiny amounts of solar noble gases managed to find their way into the mantle, presumably by solar wind irradiation of small planetesimals or dust accreting to Earth. While the moon-forming impact likely dissipated the primordial atmosphere, today´s atmosphere originated by mantle degassing and a late veneer with asteroidal and possibly cometary contributions. As other atmophile elements behave similar to noble gases, they also trace the origin of major volatiles on Earth, for example, water, nitrogen, sulfur, and carbon.
Chapitres de livres sur le sujet "C-c bond forming processes"
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Dana, Suman, M. Ramu Yadav et Akhila K. Sahoo. « Ruthenium-Catalyzed C−N and C−O Bond-Forming Processes from C−H Bond Functionalization ». Dans C-H Bond Activation and Catalytic Functionalization I, 189–215. Cham : Springer International Publishing, 2015. http://dx.doi.org/10.1007/3418_2015_126.
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Takizawa, Shinobu, et Hiroaki Sasai. « Metal-Catalyzed Enantio- and Diastereoselective C-C Bond-Forming Reactions in Domino Processes ». Dans Domino Reactions, 419–62. Weinheim, Germany : Wiley-VCH Verlag GmbH & Co. KGaA, 2013. http://dx.doi.org/10.1002/9783527671304.ch11.
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Hilterhaus, Lutz, et Andreas Liese. « Industrial Application and Processes Forming CO Bonds ». Dans Enzyme Catalysis in Organic Synthesis, 503–30. Weinheim, Germany : Wiley-VCH Verlag GmbH & Co. KGaA, 2012. http://dx.doi.org/10.1002/9783527639861.ch12.
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Zhdankin, Viktor V. « C-C-Bond Forming Reactions ». Dans Hypervalent Iodine Chemistry, 99–136. Berlin, Heidelberg : Springer Berlin Heidelberg, 2002. http://dx.doi.org/10.1007/3-540-46114-0_4.
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Shimizu, Masaki. « CC Bond-Forming Coupling Reactions ». Dans Transition-Metal-Mediated Aromatic Ring Construction, 571–616. Hoboken, NJ, USA : John Wiley & Sons, Inc., 2013. http://dx.doi.org/10.1002/9781118629871.ch22.
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Bonne, Damien, Thierry Constantieux, Yoann Coquerel et Jean Rodriguez. « Cascade Reactions Forming Both C-C Bond and C-Heteroatom BOND ». Dans Stereoselective Organocatalysis, 559–85. Hoboken, New Jersey : John Wiley & Sons, Inc., 2013. http://dx.doi.org/10.1002/9781118604755.ch16.
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Koser, Gerald F. « C-Heteroatom-Bond Forming Reactions ». Dans Hypervalent Iodine Chemistry, 137–72. Berlin, Heidelberg : Springer Berlin Heidelberg, 2002. http://dx.doi.org/10.1007/3-540-46114-0_5.
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Sako, Makoto, Shinobu Takizawa et Hiroaki Sasai. « Chapter 18. Vanadium-catalyzed Enantioselective C–C Bond-forming Reactions ». Dans Catalysis Series, 446–63. Cambridge : Royal Society of Chemistry, 2020. http://dx.doi.org/10.1039/9781839160882-00446.
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Echavarren, Antonio M., et Anna Homs. « Mechanistic Aspects of Metal-Catalyzed C,C- and C,X-Bond Forming Reactions ». Dans Metal-Catalyzed Cross-Coupling Reactions and More, 1–64. Weinheim, Germany : Wiley-VCH Verlag GmbH & Co. KGaA, 2013. http://dx.doi.org/10.1002/9783527655588.ch1.
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Klei, Steven R., Kian L. Tan, Jeffrey T. Golden, Cathleen M. Yung, Reema K. Thalji, Kateri A. Ahrendt, Jonathan A. Ellman, T. Don Tilley et Robert G. Bergman. « C—H Bond Activation by Iridium and Rhodium Complexes : Catalytic Hydrogen—Deuterium Exchange and C—C Bond-Forming Reactions ». Dans ACS Symposium Series, 46–55. Washington, DC : American Chemical Society, 2004. http://dx.doi.org/10.1021/bk-2004-0885.ch002.
Texte intégralActes de conférences sur le sujet "C-c bond forming processes"
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Seiler, P., J. Rösler, D. Mukherji et T. Kopka. « Thermal Barrier Coatings on Novel High Temperature Cobalt Rhenium Substrates ». Dans ITSC2011, sous la direction de B. R. Marple, A. Agarwal, M. M. Hyland, Y. C. Lau, C. J. Li, R. S. Lima et A. McDonald. DVS Media GmbH, 2011. http://dx.doi.org/10.31399/asm.cp.itsc2011p0926.
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Abstract Presently, highly stressed components in gas turbines are mainly made of single crystal nickel based alloys and the maximum application temperature (without coatings) is typically limited to 1100°C. Superalloys are now reaching limits posed by their melting temperatures. Increasing the substrate temperature beyond 1200°C will increase the efficiency of the turbine significantly. A new generation high temperature Co-Re alloys are aimed for use at +100°C above present single crystal nickel-superalloys. The substrates will be protected against the higher gas temperatures by thermal barrier coatings. For Co-Re alloy substrates CoReCrSi is a promising bond-coat material. CoReCrSi is thermo-chemically compatible to Co-Re due to the very similar mechanical and chemical properties. The oxide formation and the adhesion of the top coat are being investigated by studying a simplified coating system. The coating system consists of a CoReCrSi bond coat bulk material, and an yttria-stabilised zirconia top coat. The system was tested under cyclic conditions at 1200°C. This study provides a first insight into the TGO growth, the basic failure mechanism of the top coat, and the diffusion processes at the top coat/bond coat interface. It is shown that CoReCrSi with 2 at.% silicon promotes a good adhesion of the top coat by forming a dense chromium oxide layer. The critical TGO thickness beyond which the TGO fails by spallation was determined to be 25 microns and is roughly 2.5 times the critical thickness in MCrAlY based system in nickel-alloys.
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Gulizia, S., B. Tiganis, M. Z. Jahedi, N. Wright, T. Gengenbach et C. MacRae. « Effects of Cold Spray Process Gas Temperature on CP Titanium Structure ». Dans ITSC2009, sous la direction de B. R. Marple, M. M. Hyland, Y. C. Lau, C. J. Li, R. S. Lima et G. Montavon. ASM International, 2009. http://dx.doi.org/10.31399/asm.cp.itsc2009p0237.
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Abstract During cold spraying, small particles are propelled to supersonic speeds and adhere to the substrate on impact, forming a strong bond. This work examines the effect of process gas temperature on cold spray coatings produced from commercially pure (CP) titanium powders. Nitrogen gases at 400, 600, and 800 °C were used as the propellant and nitrogen and oxygen content in the titanium coating was examined. The findings suggest that at high gas temperatures, the oxygen and nitrogen in the commercially pure titanium deposits increases at the particle boundaries.
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Huang, Lingfeng, Jianming Liu, Xuying Cheng, Deming Zhang et Yueguang Yu. « The Structure and Oxidation Resistance Behavior of Ni-CrAlY Coatings Prepared by Plating Process ». Dans ITSC2018, sous la direction de F. Azarmi, K. Balani, H. Li, T. Eden, K. Shinoda, T. Hussain, F. L. Toma, Y. C. Lau et J. Veilleux. ASM International, 2018. http://dx.doi.org/10.31399/asm.cp.itsc2018p0557.
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Abstract MCrAlY(M=Ni, Co, or Ni-Co)coatings with good high temperature oxidation resistance have attracted great interest. They are widely used in gas turbines as protecting layers, such as thermal barrier coatings and seal coatings. Among many methods developed for preparing MCrAlY coatings, electroplating has drawn great attention due to its perfect bond strength, precise controllability, good coating ability for complex shape and so on. In this paper, the MCrAlY coatings have been prepared by a composite plating way. During this process, the CrAlY particles are wrapped with Ni clad layer. The thickness of the composite coatings is controlled at 150- 200 μm. The plating tests results indicate that the density of the clad layers mainly depend on the electroplating time. After that, these coatings are heat treated under the vacuum condition to make elements diffuse, forming homogeneous M(Ni)CrAlY component. The high-temperature oxidation resistance tests of the prepared coatings show good antioxidant ability at 1000 °C under air condition.
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Sakimoto, Takahiro, Tsunehisa Handa, Hisakazu Tajika, Yoshiaki Murakami et Joe Kondo. « Effect of Tensile Pre-Strain on Collapse Pressure of Coated Linepipe ». Dans ASME 2019 38th International Conference on Ocean, Offshore and Arctic Engineering. American Society of Mechanical Engineers, 2019. http://dx.doi.org/10.1115/omae2019-95923.
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Abstract As offshore pipeline projects have expanded to deeper water regions with depths of more than 2,000 m, linepipes are required to have higher resistance against collapse by external pressure. Collapse resistance is mainly controlled by the pipe geometry and compressive yield strength. In UOE pipe, the compressive yield strength along the circumferential direction changes dramatically due to tensile pre-strain that occurs in pipe forming processes such as the expansion process. In order to improve the compressive yield strength of pipes, it is important to consider the Bauschinger effect caused by pipe expansion. As the mechanism of this effect, it is understood that internal stress is generated by the accumulation of dislocations, and this reduces reverse flow stress. Compressive yield strength is also changed by the thermal cycle associated with application of fusion-bond epoxy in pipe anti-corrosion coating by the induction heating process. In the typical thermal heat cycle of this coating process, the maximum heat temperature is from 200 °C to 250 °C. In this case, compressive yield strength increases as an effect of the thermal cycle, resulting in increased collapse resistance. Thus, for deep water application of UEO linepipe, it is important to clarify the conflicting effects of the Bauschinger effect and the thermal heat cycle on compressive yield strength. Based on this background, in this study, the combined effect of the Bauschinger effect and the thermal heat cycle on compressive stress is investigated by conducting tensile pre-strain tests and simulation of the thermal cycle associated with coating. Compressive yield strength was obtained for several pre-strain and thermal cycle conditions, and the collapse pressure was calculated by an FE analysis based on the obtained compressive yield strength. This study discusses the effect of tensile pre-strain on the collapse pressure of linepipes with these simulated thermal heat cycles.
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Wang, Xueqiang, Joan G. Donaire et Ruben Martin. « Metal-Free sp2 and sp3 C-H Functionalization/C-O Bond Forming Reaction ». Dans 15th Brazilian Meeting on Organic Synthesis. São Paulo : Editora Edgard Blücher, 2013. http://dx.doi.org/10.5151/chempro-15bmos-bmos2013_2013815132216.
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Sakimoto, Takahiro, Hisakazu Tajika, Tsunehisa Handa, Yoshiaki Murakami, Satoshi Igi et Joe Kondo. « Collapse Resistance Under Combined External Pressure and Bending Deformation of Coated Linepipe ». Dans ASME 2020 39th International Conference on Ocean, Offshore and Arctic Engineering. American Society of Mechanical Engineers, 2020. http://dx.doi.org/10.1115/omae2020-18250.
Texte intégralRésumé :
Abstract As offshore pipeline projects have expanded to deeper water regions with depths of more than 2 000 m, higher resistance against collapse by external pressure is now required in linepipe. Collapse resistance is mainly controlled by the pipe geometry and compressive yield strength. In UOE pipe, the compressive yield strength along the circumferential direction changes dramatically due to tensile pre-strain that occurs in pipe forming processes such as the expansion process. In order to improve the compressive yield strength of pipes, it is important to consider the Bauschinger effect caused by pipe expansion. As the mechanism of this effect, it is understood that internal stress is generated by the accumulation of dislocations, and this reduces reverse flow stress. Compressive yield strength is also changed by the thermal cycle associated with application of fusion-bond epoxy in pipe anti-corrosion coating by induction heating. In the typical thermal heat cycle of this coating process, the maximum heating temperature is from 200 °C to 250 °C. In this case, compressive yield strength increases as an effect of the thermal cycle, resulting in increased collapse resistance. Thus, for deep water application of UEO linepipe, it is important to clarify the conflicting effects of the Bauschinger effect and the thermal heat cycle on compressive yield strength. During installation of deep water pipelines by a method such as J-lay, curvature is imposed on the pipe axis, but the circumferential bending that leads to ovalization is determined by the interaction of the curvature of bending deformation. This bending deformation decreases collapse resistance. The interaction of external pressure and bending is also important when evaluating collapse. Against this background, this study discusses the collapse criteria for coated linepipe and their bending interaction against collapse based on a full-scale collapse test under external pressure with and without bending loading. The effect of the thermal heat cycle on linepipe collapse criteria is also discussed based on the results of tensile pre-strain tests with simulation of the thermal cycle and a collapse calculation by FEA.
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Ganapathy, D., et G. Sekar. « An efficient and reusable palladium nanocatalyst in C-C bond forming cross-coupling reactions ». Dans 15th Brazilian Meeting on Organic Synthesis. São Paulo : Editora Edgard Blücher, 2013. http://dx.doi.org/10.5151/chempro-15bmos-bmos2013_201386477.
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Kang, Bruce S., et Changyu Ma. « Development of ODS Coating for Critical Turbine Components Using DED Additive Manufacturing ». Dans ASME Turbo Expo 2020 : Turbomachinery Technical Conference and Exposition. American Society of Mechanical Engineers, 2020. http://dx.doi.org/10.1115/gt2020-14874.
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Abstract The challenge for design and manufacturing of future advanced gas turbine systems is to meet the requirement of increasing turbine inlet temperature (TIT), which is higher than the substrate melting temperature. Increasing high thermal load also causes severe oxidation and corrosion of base alloy in gas turbine. Current approach is coating the inlet turbine blade with thermal barrier coating (TBC) combined with internal cooling channel in the substrate. However, neither the ceramic coating layer nor the metallic bond coat in the TBC system can provide structural loading support to house the internal cooling channels. Development of structural bond coat with embedded cooing channels can be one of the key technologies for future advanced turbine systems. In this research, high temperature protective structural coating on top of a superalloy substrate (popular for making gas turbine component) by additive manufacturing (AM) technique using oxide dispersion strengthening (ODS) powder is presented. A novel combined mechanochemical bonding (MCB) plus ball milling (BM) process is utilized to produce ODS powders suitable for AM applications. AM-processed ODS coating by direct energy deposition (DED) method on MAR-247 substrate were carried out. The ODS coated samples were then subjected to cyclic thermal loadings for over 4000 cycles (each cycle consists of alternating between 45 minutes at 1100 °C and 45 minutes at room temperature). SEM and EDX were applied for oxide formation analyses of the ODS coating at selected thermal cycles. In particular, stability of gamma prime phase in the ODS coating at different thermal cycles is analyzed. Test results revealed a thin continuous durable alumina oxide layer on ODS coating surface after over 4,000 thermal cycles. Test results also showed relatively stable substrate microstructures due to the protective alumina surface oxide layer and strong bonding at ODS coating/substrate interface is maintained. Oxidation weight gain of a AM-processed ODS sample is conducted and the results compared favorably with those literature available alumina forming alloys (AFA) under similar testing conditions.
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Bennett, Christianna. « Severing Ties : A Pedagogy for Envisioning New Typologies of Environmentally-Attuned Architecture ». Dans 112th ACSA Annual Meeting. ACSA Press, 2024. http://dx.doi.org/10.35483/acsa.am.112.31.
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The relationship between architecture and landscape must undergo fundamental change to deal with the urgency of the climate crisis, adapt to changing cultural values, and support local environmental conditions. Although there has been progress in modifying architectural construction methods and implementing the use of sustainable materials, structures continue to depend on extractive infrastructure through integrated building systems such as electricity, telecom, heating, and cooling. The ongoing reliance on extractive infrastructure bonds architecture to exploitative technologies and industries, which has fundamentally altered its relation to landscape. At present, architecture relies on an abundance of fuel from distant locations to operate, and ignores its surroundings as a result.In recent design studios, I ask students to generate alternate connections between architecture and environment. Specifically, I teach students how to critically disengage from extractive processes and systems, and instead knit architecture into local ecosystems. This is achieved through critical analysis of existing infrastructure and the design of new systems. Supported by the integration of interdisciplinary perspectives, the rewiring of systems results in new, speculative architectural typologies that engage reciprocally with complex ecologies. According to this framework, students interrogate the role architecture plays in the sustenance of the environment and are challenged to design in ways that depart from the status quo. Lessons include a) direct observation and interpretation of nature, b) translation of observations and interpretation into systems-focused interventions, c) an integrative approach linking systems and objects, and d) exercises in ‘making worlds’ and ‘futuring,’ for forming speculative narratives about architecture’s future role in the environment. By addressing these issues, architecture becomes an instrument for reimagining human relationships with nature and serves as the basis for forming new bonds with the environment.
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Zafred, Paolo R., Shay L. Harrison et Jeffrey J. Bolebruch. « Development and Testing of High Purity Alumina Ceramics for SOFC Stack Components ». Dans ASME 2010 8th International Conference on Fuel Cell Science, Engineering and Technology. ASMEDC, 2010. http://dx.doi.org/10.1115/fuelcell2010-33316.
Texte intégralRésumé :
The successful attainment of many of the next generation Siemens SOFC Advanced Module features is dependent on development of key components required to provide fuel and process air to a stack of Delta cells. The overall objectives of this development effort included design and analysis of key stack components, fabrication of low cost net shape castings, characterization of high purity alumina ceramic material, and validation through full scale testing in Single and Multi-Cell Test Articles. The manufacturing process chosen for fabrication of stack components is a unique injection molding process referred to as the Blasch process. The Blasch process is a relatively low cost manufacturing process which allows for the fabrication of complex, close tolerance, near net shapes in a range of high alumina ceramic compositions without the need for expensive secondary machining. The Blasch process allows engineers to design virtually without restrictions related to other forming processes such as slip casting, extrusion, or pressing. The process utilizes nanotechnology to strongly bind together ceramic slurries containing one of a series of proprietary binders that can be activated by utilization of specific time/temperature processing. After casting into engineered molds, the binders in these slurries are caused to precipitate irreversibly and, upon firing, form a particularly thermal shock resistant ceramic bond containing no free silica. Ceramic shapes formed in this process shrink minimally and predictably, during firing, and therefore this is one of the few processes that can be claimed as true net shape manufacturing. Considerable effort went also in the development of a new class of failure tolerant alumina ceramics for SOFC stack components for service in reducing atmosphere at temperatures up to 1000°C. Pressureless infiltration of freeze cast alumina parts with chromium oxide was conducted to improve material’s strength. Strengthening of the porous alumina matrix is postulated to be a combination of both fracture toughness increase and crack size decrease, as a result of the infiltration process. Final results suggest that mechanical properties of infiltrated ceramics are superior to conventional porous freeze cast alumina material. This paper addresses the approach to ceramic castings design for SOFC stack components, the fabrication challenges with respect to shape complexity and the experimental tests performed to validate the material choice.
Rapports d'organisations sur le sujet "C-c bond forming processes"
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Botulinum Neurotoxin-Producing Clostridia, Working Group on. Report on Botulinum Neurotoxin-Producing Clostridia. Food Standards Agency, août 2023. http://dx.doi.org/10.46756/sci.fsa.ozk974.
Texte intégralRésumé :
In 1992 a working group of the UK Advisory Committee on the Microbiological Safety of Food presented a report on Vacuum Packaging and Associated Processes regarding the microbiological safety of chilled foods. The report supported subsequent guidance provided by the UK Food Standards Agency for the safe manufacture of vacuum packed and modified atmosphere packed chilled foods. In 2021 the ACMSF requested that a new subgroup should update and build on the 1992 report as well as considering, in addition to chilled foods, some foods that are intended to be stored at ambient temperatures. The new subgroup agreed a scope that includes the conditions that support growth and/or neurotoxin formation by C. botulinum, and other clostridia, as well as identification of limiting conditions that provide control. Other foodborne pathogens that need to be considered separately and some foods including raw beef, pork and lamb were explicitly excluded. The subgroup considered the taxonomy, detection, epidemiology, occurrence, growth, survival and risks associated with C. botulinum and other neurotoxin-forming clostridia. There has been no significant change in the nature of foodborne botulism in recent decades except for the identification of rare cases caused by neurotoxigenic C. butyricum, C. baratii and C. sporogenes. Currently evidence indicates that non-clostridia do not pose a risk in relation to foodborne botulism. The subgroup has compiled lists of incidents and outbreaks of botulism, reported in the UK and worldwide, and have reviewed published information concerning growth parameters and control factors in relation to proteolytic C. botulinum, non-proteolytic C. botulinum and the other neurotoxigenic clostridia. The subgroup concluded that the frequency of occurrence of foodborne botulism is very low (very rare but cannot be excluded) with high severity (severe illness: causing life threatening or substantial sequelae or long-term illness). Uncertainty associated with the assessment of the frequency of occurrence, and with the assessment of severity, of foodborne botulism is low (solid and complete data; strong evidence in multiple sources). The vast majority of reported botulism outbreaks, for chilled or ambient stored foods, are identified with proteolytic C. botulinum and temperature abuse is the single most common cause. In the last 30 years, in the UK and worldwide where a cause can be identified, there is evidence that known controls, combined with the correct storage, would have prevented the reported incidents of foodborne botulism. The subgroup recommends that foods should continue to be formulated to control C. botulinum, and other botulinum neurotoxin-producing clostridia, in accordance with the known factors. With regard to these controls, the subgroup recommends some changes to the FSA guidelines that reflect improved information about using combinations of controls, the z-value used to establish equivalent thermal processes and the variable efficacy associated with some controls such as herbs and spices. Current information does not facilitate revision of the current reference process, heating at 90°C for 10 minutes, but there is strong evidence that this provides a lethality that exceeds the target 6 order of magnitude reduction in population size that is widely attributed to the process and the subgroup includes a recommendation that the FSA considers this issue. Early detection and connection of cases and rapid, effective coordinated responses to very rare incidents are identified as crucial elements for reducing risks from foodborne botulism. The subgroup recommends that the FSA works closely with other agencies to establish clear and validated preparedness in relation to potential major incidents of foodborne botulism in the UK.