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Showing 1 to 20 of 165 for “"nucleophile"”.
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Enantioselective nucleophile-catalyzed cycloadditions
… 1 describes the development of an asymmetric nucleophile-catalyzed [2+2] cycloaddition of ketenes with aldehydes. This is the first report of a catalytic enantioselective synthesis of trisubstituted [beta]-lactones. Two enantioselective phosphine-catalyzed [3+2] cycloadditions of allenoates …
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Nucleophile Reaktivität von Diazoverbindungen und stabilisierten Carbanionen
… und Chinonmethiden) wurde genutzt, um die nucleophile Reaktivität unterschiedlicher Substanzklassen zu vergleichen. Zu diesem Zweck wurde die Kinetik der Reaktionen von Benzhydrylkationen mit Diazoverbindungen photometrisch in Dichlormethan untersucht. In analoger Weise wurden die …
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Nucleophile Reaktivität von Wittig-Yliden, phosphorylstabilisierten Carbanionen und anorganischen Anionen
… der Reaktivität von Elektrophilen und Nucleophilen. Dies ermöglichte im 2. Teil der Arbeit, die Nucleophilie von Wittg-Yliden, Wadsworth-Horner-Emmons- und Horner-Wittig-Reagenzien zu bestimmen und Aussagen zu Vorhersagbarkeit der Geschwindigkeit ihrer Olefinierungsreaktionen zu …
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Studies of Nucleophilic Substitution at Neutral Nitrogen
… reaction in which the transition state has the nucleophile and leaving group associated with nitrogen and an ionization process involving the initial formation of a nitrenium ion-pair which is subsequently attacked by the nucleophile.
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Activated Phosphate Reagents for the Synthesis of Functionalized Oligophosphates
… which react with a wide variety of nucleophiles to generate a library of oligophosphate products ranging from triphosphates to pentaphosphates. Furthermore, preliminary studies were undertaken to further elaborate the roles these oligophosphate play in biology. Trimetaphosphate …
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Reactivity of the Vinylogous Epoxyketone Moiety
… results obtained from adding various nucleophiles. A hard nucleophile, phenyl lithium, was shown to add according to predications based on the HSAB theory. The reactivity of a soft nucleophile, the enolate of diethyl malonate, was not explained by the HSAB theory but by other factors …
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A structure-reactivity study of selected phosphorus compounds
… The angular dependence of the approach of nucleophiles to quaternary phosphonium ions L₄P+ was investigated. The analysis of 36 structures of the general formula L₄P+X- indicates that the nucleophile generally adopts the "face" approach to the phosphonium centre. When the expected leaving …
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The immobilisation of Thermus strain Rt41A proteinase and its use in peptide synthesis
… Phe-NH₂, Leu-pNA and Val-pNA were all reactive nucleophiles. The substrate specificity for peptide synthesis was therefore very similar to that found for hydrolysis reactions. The synthesis of Bz-Ala-Tyr-NH2 was optimised by studying the effect of pH, temperature, solvent concentration, ionic …
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Development and investigation of novel chemoselective processes in Pd and Cu catalysis
… one will describe the development of dual nucleophile/electrophile chemoselectivity in the Suzuki-Miyaura reaction. Chemoselectivity in this key crosscoupling reaction has previously only been achieved at either the nucleophile or the electrophile independently. Electrophile …
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Studies on the Total Synthesis of (+/-)-Cameroonan-7alpha-Ol and Presilphiperfolan-8-Ol and Discovery of a Novel Stereoselective Prins Cyclization of Delta,epsilon-Unsaturated Ketones
… rationalized by intramolecular delivery of the nucleophile.
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Synthesis of Selenium-Alkylated Selenocysteine Derivatives and Their Use in Native Chemical Ligation, Expressed Protein Ligation and the Synthesis of Dehydropeptides
… peptide acted as a Michael acceptor for a thiol nucleophile. These solid phase reactions were monitored by magic angle spinning NMR spectroscopy.
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Model Compounds for the Photoactivation of Glycosyl Donors
… an oxonium intermediate that may alkylate other nucleophiles, which should be analogous to a glycosylation reaction. It was determined that a moiety with an internal sensitizer could photochemically exchange a tetrahydropyran at 300 nm. It was also determined that 6- methylhex-5-en-1-ol-THP …
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A Study of the Structure Of 1,1,2,2-Tetracyanocyclopropane-Methanol Adduct
… for homoconjugate addition to occur between a nucleophile and a cyclopropane, it was necessary for the cyclopropane to contain two activating groups, such as -COCR or -CN. The initial intent of this research was to investigate the possibility of similar reactions with 1,1,2,2- …
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Catalytic allylation of aldehydes mediated via the water-gas shift reaction
… an expansion of the scope of the allyl pro-nucleophile as a way to both improve the synthetic utility of the reaction and explore steric and electronic effects of the allyl pro-nucleophile on the course of the reaction. This effort resulted in the successful application of five different …
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Evolvability of a viral protease: experimental evolution of catalysis, robustness and specificity
… of core active site machinery, I mutated the nucleophile of TEV to serine. The differing chemical properties of oxygen and sulphur force the enzyme into a fitness valley with a >104-fold activity reduction. Nevertheless, directed evolution was able to recover function, resulting in an enzyme …
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Novel Liquid extraction method for detecting Native-wood Formaldehyde
… a complete formaldehyde extraction, a stronger nucleophile than hydroxyl and water groups is needed. In this study cross-linked poly (allylamine) (PAA) beads were synthesized and used as a strong nucleophile to extract all the biogenic and synthetic free-formaldehyde within the woody matrix of …
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Radical methods for the synthesis of aliphatic amines
… agent. The use of a carboxylic acid derived nucleophile enabled a broader scope in both amine and nucleophile components and the full potential of this reaction is currently being developed. In chapter 4, a visible light-mediated direct synthesis of N-heterospirocycles is reported. A …
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Investigating carbocations using high speed ball milling
… of secondary alkyl halides depend on the nucleophile. However, reactions that form a carbocation intermediate, such as, S<sub>N</sub>1 reaction and pinacol rearrangement have not been explored, until now.
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Novel Conjugate Additions and Cyclizations on Multiyne Systems
… strategy wherein acetyl ketene is activated by a nucleophile connected to the 1,3-diynone moiety. This tethering promotes a sequential 1,6-addition with a C-nucleophile followed by a 1,4-addition with an O-nucleophile to generate 2-methylene-2H-pyrans. In the second approach, a zwitterionic …
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Precursor-Directed Identification of Natural Product Scaffolds
… analog via incorporation of a carbon-based nucleophile.
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