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Auswahl der wissenschaftlichen Literatur zum Thema „C-N bond forming processes“
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Zeitschriftenartikel zum Thema "C-N bond forming processes"
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Valdés, Carlos, Raquel Barroso und María Cabal. „Pd-catalyzed Auto-Tandem Cascades Based on N-Sulfonylhydrazones: Hetero- and Carbocyclization Processes“. Synthesis 28, Nr. 19 (10.08.2017): 4434–47. http://dx.doi.org/10.1055/s-0036-1588535.
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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
2
Buchspies, Jonathan, Md Mahbubur Rahman und 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, Nr. 1 (02.01.2021): 188. http://dx.doi.org/10.3390/molecules26010188.
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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.
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Correa, Arkaitz, und Marcos Segundo. „Cross-Dehydrogenative Coupling Reactions for the Functionalization of α-Amino Acid Derivatives and Peptides“. Synthesis 50, Nr. 15 (25.06.2018): 2853–66. http://dx.doi.org/10.1055/s-0037-1610073.
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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
4
Youn, So Won. „Transition-Metal-Catalyzed Annulative Coupling Cascade for the Synthesis of 3-Methyleneisoindolin-1-ones“. Synthesis 52, Nr. 06 (15.01.2020): 807–18. http://dx.doi.org/10.1055/s-0039-1690046.
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This short review describes the recent progress made on transition-metal-catalyzed annulative couplings for the synthesis of 3-methyleneisoindolin-1-ones, which are useful intermediates for the synthesis of numerous alkaloids and can be often found in a wide range of natural products and pharmaceuticals. In particular, new one-pot multiple C–C/C–N bond-forming processes for the construction of the 5-methylenepyrrol-2-one nucleus of such compounds are summarized.1 Introduction2 Intramolecular Cyclization Reactions: C3–N or C3–C3a and C–C Bond Formation3 Intermolecular Annulative Coupling Reactions3.1 C3–C3a and C3–N Bond Formation3.2 C1–C7a and C3–N Bond Formation3.3 C1–C7a and C1–N Bond Formation3.4 C1–C7a, C1–N and C3–N Bond Formation3.5 C3–C3a, C1–C7a, C1–N and C3–N Bond Formation: A Pd-Catalyzed One-Pot Sonogashira Coupling–Carbonylation–Amination–Cyclization Cascade4 Conclusion
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Martín, Cristina del Mar García, José Ignacio Hernández García, Sebastián Bonardd und David Díaz Díaz. „Lignin-Based Catalysts for C–C Bond-Forming Reactions“. Molecules 28, Nr. 8 (16.04.2023): 3513. http://dx.doi.org/10.3390/molecules28083513.
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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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McNally, Andrew, Ryan Dolewski und Michael Hilton. „4-Selective Pyridine Functionalization Reactions via Heterocyclic Phosphonium Salts“. Synlett 29, Nr. 01 (12.12.2017): 08–14. http://dx.doi.org/10.1055/s-0036-1591850.
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Pyridines are widely used across the chemical sciences in applications ranging from pharmaceuticals, ligands for metal complex and battery technologies. Direct functionalization of pyridine C–H bonds is an important strategy to make useful pyridine derivatives, but there are few ways to selectively transform the 4-position of the scaffold. We recently reported that pyridines can be converted into heterocyclic phosphonium salts that can serve as generic handles for multiple subsequent bond-forming processes. Reactions with nucleophiles and transition-metal cross-couplings will be described to make C–O, C–S, C–N, and C–C bonds in a diverse range of pyridines including those embedded in complex pharmaceuticals.1 Introduction2 Direct, Regioselective Functionalization of Pyridines3 4-Position Selectivity via Metal Catalysis4 Versatile Functional Groups versus Specific Bond Constructions5 Phosphonium Salts as Reagents for Pyridine Functionalization6 Conclusions
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Daoust, Benoit, Nicolas Gilbert, Paméla Casault, François Ladouceur und Simon Ricard. „1,2-Dihaloalkenes in Metal-Catalyzed Reactions“. Synthesis 50, Nr. 16 (09.07.2018): 3087–113. http://dx.doi.org/10.1055/s-0037-1610174.
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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 und John Montgomery. „Deoxygenative C–C Bond-Forming Processes via a Net Four-Electron Reductive Coupling“. Journal of the American Chemical Society 137, Nr. 40 (05.10.2015): 12788–91. http://dx.doi.org/10.1021/jacs.5b08448.
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Liu, Jialin, Xiaoyu Xiong, Jie Chen, Yuntao Wang, Ranran Zhu und Jianhui Huang. „Double C–H Activation for the C–C bond Formation Reactions“. Current Organic Synthesis 15, Nr. 7 (16.10.2018): 882–903. http://dx.doi.org/10.2174/1570179415666180720111422.
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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 und John Montgomery. „ChemInform Abstract: Deoxygenative C-C Bond-Forming Processes via a Net Four-Electron Reductive Coupling.“ ChemInform 47, Nr. 12 (März 2016): no. http://dx.doi.org/10.1002/chin.201612061.
Der volle Inhalt der QuelleDissertationen zum Thema "C-N bond forming processes"
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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.
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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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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/.
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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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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.
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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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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.
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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.
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Brace, Gareth Neil. „Applications of palladium-catalysed C-N bond forming reactions“. Thesis, University of Bath, 2006. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.428381.
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Graham, Alan. „New C-C and C-N bond forming reactions mediated by chromium complexation“. Thesis, University of Bath, 1996. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.760696.
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Fabris, Massimo <1980>. „Innovative green methodologies for C-C, C-N and C-O bond forming reactions“. Doctoral thesis, Università Ca' Foscari Venezia, 2011. http://hdl.handle.net/10579/1096.
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In questo lavoro di tesi è riportato l'impiego di alcuni strumenti della Green Chemistry (come la CO2, i liquidi ionici e i dialchilcarbonati) per la messa a punto di metodologie innovative a ridotto impatto ambientale per la formazione di legami C-C, C-N e C-O. Sono state investigate le seguenti reazioni: la metatesi dell'1-ottene catalizzata da sistemi a base di Re ossido, in presenza di CO2 densa come solvente; l'addizione di Michael di nitroalcani e beta-dichetoni a chetoni alfa,beta-insaturi catalizzata da liquidi ionici; la selettiva mono-idrossialchilazione di aniline con la glicerina carbonato, catalizzata da faujasiti; la selettiva bis-N-alchilazione di aniline da parte del dimetilcarbonato prodotto in situ via transesterificazione di carbonati ciclici con metanolo, catalizzata da faujasiti; l'alchilazione di aniline con carbonati ciclici catalizzata da liquidi ionici; la reazione di decarbossilazione dei dialchilcarbonati in presenza di diversi catalizzatori eterogenei; la reazione tra fenolo e glicerina carbonato catalizzata da faujasiti.In this PhD thesis it is presented the use of some Green Chemistry Tools (supercritical carbon dioxide, ionic liquids and dialkylcarbonates) for the set up of new green methodologies for C-C, C-N and C-O bond forming reactions. The following reactions have been investigated: the self-metathesis of 1-octene catalysed by supported Re oxide systems, carried out using dense CO2 as solvent; the Michael addition of nitroalkanes and beta-diketones to alpha,beta-unsaturated ketons catalyzed by task specific phosphonium based ionic liquids; the selective mono-hydroxyalkylation of anilines with glycerol carbonate catalysed by alkali metal exchanged faujasites; the selective bis-N-methylation of anilines carried by dimethylcarbonate prepared in situ via the transesterification of alkylene carbonate with methanol catalysed by alkali metal exchanged faujasites; the alkylation of primary aromatic amines with alkylene carbonates, catalysed by phosphonium based ionic liquids; the decarboxylation reaction of dialkyl carbonates catalyzed by different heterogeneous systems; the reaction of glycerol carbonate with phenol, in the presence of faujasites as catalysts.
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Pawlikowski, Andrew V. „Developments in late metal-mediated C-N bond forming reactions /“. Thesis, Connect to this title online; UW restricted, 2006. http://hdl.handle.net/1773/8489.
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Anderson, Kevin William. „Expanding the substrate scope in palladium-catalyzed C-N and C-C bond-forming reactions“. Thesis, Massachusetts Institute of Technology, 2006. http://hdl.handle.net/1721.1/36255.
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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Chemistry, 2006.Vita.
Includes bibliographical references.
Chapter 1. The first detailed study of the palladium-catalyzed amination of aryl nonaflates is reported. Use of bulky electron-rich monophosphinobiaryl ligands or BINAP allow for the catalytic amination of electron-rich and -neutral aryl nonaflates with both primary and secondary amines. Using XantPhos, the catalytic amination of a variety of functionalized aryl nonaflates resulted in excellent yields of anilines; even 2-carboxymethyl aryl nonaflate is effectively coupled with a primary alkyl amine. Moderate yields were obtained when coupling halo-aryl nonaflates with a variety of amines, where in most cases the aryl nonaflate reacted in preference to the aryl halide. Overall, aryl nonaflates are an effective alternative to aryl triflates in palladium-catalyzed C-N bond-forming processes due to their increased stability under the reaction conditions. Chapter 2. A catalyst comprised of a Pd precatalyst and 2-dicyclohexylphosphino-2',4',6'-triisopropylbiphenyl is explored in C-N bond-forming processes. This catalyst displayed unprecedented stability and scope allowing, for the first time, the coupling of substrates bearing a carboxylic acid or a primary amide.
(cont.) Also, the more bulky catalyst system Pd/2-tert-butylphosphino-2',4',6'-triisopropylbiphenyl was found to be effective for the Narylation of 2-aminoheterocycles and weakly basic HN-heterocycles: pyrazole and indazole. The chemoselectivity for amination using these catalysts was explored where the rough order of reactivity for amines is: aryl amines >> primary and secondary alkyl amines > 2-aminoheterocycles > primary amides - HN-heterocycles. Chapter 3. The palladium-catalyzed Suzuki-Miyaura coupling of haloaminoheterocycles and functionalized organoboronic acids using a highly active and stable monophosphinobiaryl ligand, 2-dicyclohexylphosphino-2',6'-dimethoxybiphenyl, efficiently produced aminoheterocyclic biaryl derivatives. This same catalyst was effective in coupling 2-haloaminoaryl compounds with 2-formyl or 2-acetylphenyl boronic acids, providing the fused heterocyclic compounds phenanthridine, benzo[c][1 ,8]naphthridine and benzo[c][1,5]naphthridine in excellent yields. Chapter 4. A water-soluble monophosphinobiaryl ligand, sodium -dicyclohexylphosphino-2',6'-dimethoxybiphenyl-3'-sulfonate, was synthesized by electrophilic sulfonation of the lower-aromatic ring of 2-dicyclohexylphosphino-2',6'- dimethoxybiphenyl.
(cont.) This ligand was utilized in the palladium-catalyzed Suzuki-Miyaura reaction of water-soluble aryl/heteroaryl halides and organoboronic acids. The catalyst displays unprecedented reactivity and stability for Suzuki-Miyaura reactions conducted in water. Chapter 5. A water-soluble monophosphinobiaryl ligand, sodium 2'-(dicyclohexyl-osphanyl)-2,6-diisopropyl-biphenyl-4-sulfonate, was synthesized by a proposed electrophilic ipso-substitution/reverse Friedel-Crafts alkylation of the lower-aromatic ring on 2-dicyclohexylphosphino-2',4',6'-triisopropylbiphenyl. This ligand was utilized in the palladium-catalyzed Heck alkynylation (copper-free Sonogashira coupling) of hydrophobic and hydrophilic aryl halides and terminal alkynes conducted in an aqueous acetonitrile solvent system. For the first time, an electron-deficient terminal alkyne, propiolic acid, was successfully coupled with aryl bromides. We also demonstrated that this catalyst is useful in the reaction of benzyl chlorides and terminal alkynes to provide benzyl alkynes in good yields. We show that by using an excess amount of base (> 1.0 equiv.) and higher reaction temperatures ( 80 °C), base-catalyzed isomerization to the corresponding aryl allenes can be achieved in a one-pot process.
by Kevin W. Anderson.
Ph.D.
Buchteile zum Thema "C-N bond forming processes"
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Dana, Suman, M. Ramu Yadav und Akhila K. Sahoo. „Ruthenium-Catalyzed C−N and C−O Bond-Forming Processes from C−H Bond Functionalization“. In 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, und Hiroaki Sasai. „Metal-Catalyzed Enantio- and Diastereoselective C-C Bond-Forming Reactions in Domino Processes“. In 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, und Andreas Liese. „Industrial Application and Processes Forming CO Bonds“. In 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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Lemen, Georgia S., und John P. Wolfe. „Palladium-Catalyzed sp2 C–N Bond Forming Reactions: Recent Developments and Applications“. In Amination and Formation of sp2 C-N Bonds, 1–53. Berlin, Heidelberg: Springer Berlin Heidelberg, 2012. http://dx.doi.org/10.1007/3418_2012_56.
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Wolfe, John P., Joshua D. Neukom und Duy H. Mai. „Synthesis of Saturated Five-Membered Nitrogen Heterocycles via Pd-Catalyzed CN Bond-Forming Reactions“. In Catalyzed Carbon-Heteroatom Bond Formation, 1–34. Weinheim, Germany: Wiley-VCH Verlag GmbH & Co. KGaA, 2010. http://dx.doi.org/10.1002/9783527633388.ch1.
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Kannan, Masanam, Mani Sengoden und Tharmalingam Punniyamurthy. „Transition Metal-Mediated Carbon-Heteroatom Cross-Coupling (C-N, C-O, C-S, C-Se, C-Te, C-P, C-As, C-Sb, and C-B Bond Forming Reactions)“. In Arene Chemistry, 547–86. Hoboken, NJ: John Wiley & Sons, Inc, 2015. http://dx.doi.org/10.1002/9781118754887.ch20.
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Kantam, Mannepalli Lakshmi, Chintareddy Venkat Reddy, Pottabathula Srinivas und Suresh Bhargava. „Recent Developments in Recyclable Copper Catalyst Systems for C–N Bond Forming Cross-Coupling Reactions Using Aryl Halides and Arylboronic Acids“. In Amination and Formation of sp2 C-N Bonds, 119–71. Berlin, Heidelberg: Springer Berlin Heidelberg, 2013. http://dx.doi.org/10.1007/3418_2012_58.
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Lu, X. L., B. Wang und S. Chiba. „1.8 Nitrogen-Centered Radicals“. In Free Radicals: Fundamentals and Applications in Organic Synthesis 1. Stuttgart: Georg Thieme Verlag KG, 2021. http://dx.doi.org/10.1055/sos-sd-234-00146.
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AbstractNitrogen-containing compounds are prevalent in the key components of various functional materials and compounds such as pharmaceutical drugs. Therefore, it is extremely important to develop versatile synthetic methodologies capable of constructing C—N bonds in an efficient manner under milder reaction conditions. Apart from common ionic C—N bond-forming reactions (i.e., nucleophilic and electrophilic amination, as well as transition-metal-catalyzed C—N cross-coupling processes), leveraging of nitrogen-centered radicals for C—N bond-forming process has created another dimension to the modern synthesis of nitrogen-containing compounds. In particular, recent development of novel catalytic strategies and the design of new nitrogen-radical precursors have rendered their generation and use for C—N bond formation more practical and user-friendly for synthesis of wider array of nitrogen-containing compounds of potential use. This chapter highlights the latest developments in synthetic methods for C—N bond construction using nitrogen-centered radicals by showing selected reactions, mostly reported in the last five years, based on their structural and reactivity features as well as the method of radical generation.
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„Synthetic Methods for Primary Anilines“. In Methods and Strategies for C–N Bond Formation Reactions, 145–221. Royal Society of Chemistry, 2023. http://dx.doi.org/10.1039/bk9781837672615-00145.
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Aryl amines have received significant interest because these compounds widely exist in the structural backbones of ligands, pharmaceuticals, agrochemicals, natural products, and functional materials. In N-arylation reactions, several types of organic electrophile coupling partners such as (pseudo)halides (Ullmann-type and Buchwald–Hartwig couplings) and boronic acids (Chan–Lam coupling) are popular. The main synthetic methods for the preparation of these compounds involving N-arylation utilize aryl halides. Progress has been made with the coupling of arylating reagents which are less expensive than aryl halides, providing both a cost-effective and more efficient reaction route. For example, the process of C–H bond activation/functionalization, a step-efficient and atom-economical transformation, has emerged as a powerful strategy in C–N bond-forming reactions. Moreover, a transition-metal-free method for the N-arylation of amines using an aryne intermediate has been developed. This chapter focuses on recent advances in chemo- and regioselective N-arylation (either on one N-center or on the exocyclic N-site of the ring) or the selective arylation of amino alcohols without additional protection/deprotection using arylating reagents. This chapter provides an overview of arylating reagents for N-arylation reactions found in both basic and applied chemical research. The substrate scope, limitations, reaction mechanism, and chemoselectivity, as well as related control strategies of these reactions, are discussed. To the best of our knowledge, there has been no book about introducing arylating reagents to develop more efficient and environmentally friendly cross-coupling methods for the N-arylation of amines. We believe this critical review will provide necessary background information on the N-arylation of amines.
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„Well-Defined (NHC)Pd (II) Complexes and Their Use in C–C and C–N Bond-Forming Reactions“. In Process Chemistry in the Pharmaceutical Industry, Volume 2, 255–72. CRC Press, 2007. http://dx.doi.org/10.1201/9781420008357-20.
Der volle Inhalt der QuelleKonferenzberichte zum Thema "C-N bond forming processes"
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Seiler, P., J. Rösler, D. Mukherji und T. Kopka. „Thermal Barrier Coatings on Novel High Temperature Cobalt Rhenium Substrates“. In ITSC2011, herausgegeben von B. R. Marple, A. Agarwal, M. M. Hyland, Y. C. Lau, C. J. Li, R. S. Lima und 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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Saigal, Anil, Seneca Jackson Velling, Akash Dhawan, Maria Azcona Baez, Miguel Nocum und Julia R. Greer. „Fabricating Machine Elements Using Hydrogel-Infused Additive Manufacturing (HIAM)“. In ASME 2023 Aerospace Structures, Structural Dynamics, and Materials Conference. American Society of Mechanical Engineers, 2023. http://dx.doi.org/10.1115/ssdm2023-107356.
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Abstract Additive manufacturing (AM) of metals can enable rapid development of functional parts of complex geometry, with potential applications in the aerospace, automotive, and biomedical fields [1–3]. Typical metal additive manufacturing techniques are based on expensive laser melting or sintering processes which are often highly anisotropic, limiting the development and use of these methods. Furthermore, few additive manufacturing techniques focus on high temperature materials, ceramics, and fabrication of machine elements. The recent introduction of Hydrogel-Infusion Additive Manufacturing (HIAM) may reduce some of these barriers, enabling potential applications in high performance metal and ceramic devices and components. The HIAM process involves 3D printing a polyethylene oxide (PEO) photo-resin using vat polymerization, immersing the polymer in a metal salt solution which allows ionized metal cations to bond to the polymer backbone, followed by calcination to combust the polymer leaving a metal oxide that takes the same functional structure as the original polymer. Finally, the metal oxide is reduced using a forming gas (95% N2/5% H2) to give a metal product that maintains a scaled-down version of the complex as-printed architecture. This technique enables architected features with microscale resolution by use of a single photoresin simply by varying post-processing conditions. As a first step in the fabrication of machine elements and devices, this paper outlines an attempt to fabricate springs made from silver metal via HIAM. Silver nitrate is infused into an additively manufactured polymer spring structure. Based on the relative differences in the standard free energy of the oxides, Silver Oxide (AgO) is readily reduced to metallic silver under a single thermal processing step: calcination/reduction at 500°C without the need for forming gas. A variety of analytical techniques confirm HIAM processing obeys chemical kinetics of single-step calcination and reduction in accordance with literature and results in fabricated components of low microstrain (8.40E−7 ± 2.78E−9) crystalline silver with average crystallite size of 514.95 ± 5.32 Å and lattice parameter of 4.09 ± 5.23E−5 Å. Thermal analyses such as Thermogravimetric Analysis (TGA) and Differential Scanning Calorimetry (DSC) elucidate the mass loss and reactions that occur during the furnace processing. Springs were subjected to quasi-static and cyclic loading using a Dynamic Mechanical Analyzer (DMA). A range of ∼2–20 N/mm stiffness was measured in unloading for different coil diameters and produced springs show consistency of part stiffness following compaction under cyclic loading.
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Sakimoto, Takahiro, Tsunehisa Handa, Hisakazu Tajika, Yoshiaki Murakami und Joe Kondo. „Effect of Tensile Pre-Strain on Collapse Pressure of Coated Linepipe“. In 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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Sakimoto, Takahiro, Hisakazu Tajika, Tsunehisa Handa, Yoshiaki Murakami, Satoshi Igi und Joe Kondo. „Collapse Resistance Under Combined External Pressure and Bending Deformation of Coated Linepipe“. In 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.
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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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Zafred, Paolo R., Shay L. Harrison und Jeffrey J. Bolebruch. „Development and Testing of High Purity Alumina Ceramics for SOFC Stack Components“. In ASME 2010 8th International Conference on Fuel Cell Science, Engineering and Technology. ASMEDC, 2010. http://dx.doi.org/10.1115/fuelcell2010-33316.
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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.
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Miglietti, Warren, Juan Escudero, Julio Lanza, Ian Summerside und Zaki Zainuddin. „Repair Process Technology Development and Experience of Frame 7FA+E, Stage 1 Turbine Buckets“. In ASME 2011 Turbo Expo: Turbine Technical Conference and Exposition. ASMEDC, 2011. http://dx.doi.org/10.1115/gt2011-46766.
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The 60 Hz, Frame 7F engine has been in commercial operation for more than two decades now with approximately 600 Frame 7 (F, FA, FA+ and FA+e models) machines existing in North America and a total of over 1100 F-class machines throughout the world. Volatile market dynamics in the electrical power generation field continues to force power companies to identify prudent material cost reductions opportunities in their Operations and Maintenance (O&M) business. Today, there is an industry-recognized need for advanced hot gas path component repair and reconditioning capability for operators of F-Class gas turbines that can be highly cost effective with short cycle times. The first stage buckets of the Frame 7F engine are unshrouded; whereas the next 2 stages are shrouded. Out of these rotating components, the first stage buckets show the worst degradation and thus repair of these components have been a focus point for Power Systems Mfg., LLC (PSM). The technical objective is to develop a comprehensive set of repair schemes for the stage 1 buckets since these components have the highest frequency of replacement. Listed below are some of the special repair processes that have been developed for the first stage bucket: a) Acid stripping of the MCrAlY coating (and internal aluminide coating having endured 48,000 hours of service). b) High speed grinding off of the electron beam (EB) or laser beam (LB) welded tip cover plates. c) High frequency gas tungsten arc (GTA) weld repairs of platform cracks using a new and novel developed high strength yet ductile weld filler metal. d) High frequency gas tungsten arc weld attachment of new tip cover plates. e) Laser metal forming/cladding of new squealer tips. f) Rejuvenation heat treatment for buckets that have reached 48,000 hours. g) Application of new internal aluminide coating. h) Application of upgrade design features, such as platform cooling and platform undercut. i) Application of a superior MCrAlY bond coating to that of the Original Engine Manufacturer (OEM). j) Application of a vertically cracked high density (VCHD) strain tolerant thermal barrier coating (TBC). This technical paper describes the repair development process, the implementation of the different stages of the repair schemes and presents metallurgical and mechanical characteristics of the repaired regions of the component.
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Gulizia, S., B. Tiganis, M. Z. Jahedi, N. Wright, T. Gengenbach und C. MacRae. „Effects of Cold Spray Process Gas Temperature on CP Titanium Structure“. In ITSC2009, herausgegeben von B. R. Marple, M. M. Hyland, Y. C. Lau, C. J. Li, R. S. Lima und 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 und Yueguang Yu. „The Structure and Oxidation Resistance Behavior of Ni-CrAlY Coatings Prepared by Plating Process“. In ITSC2018, herausgegeben von F. Azarmi, K. Balani, H. Li, T. Eden, K. Shinoda, T. Hussain, F. L. Toma, Y. C. Lau und 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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Bennett, Christianna. „Severing Ties: A Pedagogy for Envisioning New Typologies of Environmentally-Attuned Architecture“. In 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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Kang, Bruce S., und Changyu Ma. „Development of ODS Coating for Critical Turbine Components Using DED Additive Manufacturing“. In 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.