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Showing 1 to 18 of 18 for “"umpolung"”.
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EXPLORATIONS IN MEDIUM-RING ETHER SYNTHESIS VIA UMPOLUNG HETEROATOM ACTIVATION: TOTAL SYNTHESIS, METHODS DEVELOPMENT, AND REAGENT SYNTHESIS
… to the challenging cyclic ether scaffold via umpolung reactivity of cyclic alcohols.This dissertation provides the unified synthesis and isolation of various electronically and sterically distinct N-HVIs to promote their continued investigation in the Wengryniuk group as well as synthetic …
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1. C-C Bond Formation via Soft Enolization and Umpolung-like Chemistry 2. Electrophilic Fluorination of Organozinc Reagents
… towards C-C bond formation, soft enolization and Umpolung-like chemistry. The direct synthesis of 1,3-diketones and β-keto thioesters using in good yields and with wide substrate tolerance was possible using our soft enolization strategy using crude acyl chlorides. Another C-C bond strategy …
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Synthetic and Mechanistic Investigation of Alpha-Amido Carbanions
… to effect substitution at that site provides umpolung of the customary amine polarity. This thesis reports the use of a carbonyl moiety to aid in the stabilization of negative charge adjacent to nitrogen. The syntheses of ten different N,N-dialkyl amide systems are reported, five of which have …
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Design and Synthesis of Chiral Triazolium and Thiazolium Salts Incorporating Hydrogen-Bonding Motifs as Organocatalysts
… (NHC) catalysts have been developed for use in umpolung reactions between aldehydes and a range of coupling partners. However, stereoselectivity of the new chiral centre is dif cult to control: current existing methods employ steric hindrance of catalysts to in uence this, potentially at the …
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Application of Density Functional Theory to Study the Mechanism of Alkali Metal Enolate Oxidation by N-sulfonyloxaziridines, Umpolung Amide Synthesis from Halo-Amino-Nitro Alkanes, Alkali-Metal Catalyzed Transfer Hydrogenation of Ketones, and Asymmetric Catalyzed Aza-Henry Reactions
… in a SN¬1 rather than SN¬2 like fashion. (2) umpolung amide synthesis working from 1,1,1,1-halo-amino-nitro-alkanes leading to the finding that the amide oxygen originates from the nitro group but also from explicitly interacting water molecules in competing pathways. (3) alkali (Li+, Na+, and …
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Progress in nucleophilic catalysis and development of nickel-catalyzed cross-couplings of propargylic halides
… of Michael acceptors, and represents a novel umpolung process catalyzed by N-heterocyclic carbenes. The second section discusses the first successful phosphine-catalyzed, y-alkylation reaction of isomerizable allenoates. A highly enantioselective variant of this reaction is described. Chapter …
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The Development of Palladium and Cobalt-Catalyzed Methods for the Syntheses of alpha-Trifluoromethyl and Alkyl Amines
… for the construction of this functionality. Umpolung methods are robust technologies that enable streamlined synthesis of different types of chiral amines that are more challenging to obtain with a normal polarity approach. For example, the addition of nucleophiles to electrophilic imines, …
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Polarity Inversion in Silicon and Phosphorus Compounds
… are atypical for these p-block elements. This umpolung approach affords novel reactivity that was previously unavailable to silicon and phosphorus molecules. In a first demonstration, synthetic and mechanistic studies of the 1,3-dipolar reaction of nitroarenes with geometrically constrained …
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Nucleophilic Addition to Azoalkenes; Diastereoselective Synthesis of β-Hydroxy Ketones and β,γ-Fused γ-Lactams
… part of the dissertation, we describe how an umpolung strategy that involves the addition of Grignard reagents to α-epoxy N-sulfonyl hydrazones–directed by the alkoxide of 1-azo-3-alkoxy propenes formed in situ via base-induced ring opening of the epoxide–leads to the syn-selective production …
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Design and Development of New Catalytic Carbon-Carbon Bond Forming Reactions: I. N-Heterocyclic Carbene Based Catalytic Platform for Hauser-Kraus Annulations II. Copper-Catalyzed Selective Allylic Alkylation of Allylic Systems Using Grignard Reagents
… this traditional reaction based on NHC-mediated umpolung chemistry. The method provides a milder protocol for the synthesis of polycyclic aromatic compounds and also eliminates the drawbacks of the traditional Hauser-Kraus annulation. Secondly, the development of a series of general but highly …
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Unique approaches towards the synthesis of polycyclic sesquiterpene targets
… synthesis of the common intermediate involved an umpolung conjugate addition strategy. Towards this aim, a robust and versatile set of protocols have been developed to provide access to both the racemic and asymmetric variants of this compound. Towards the construction of the key tricyclic core of …
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New Strategies and Transformations for the alpha-Functionalization of Amines to Access Chiral Amines
… known process mechanism, we first explored the umpolung functionalization of amines through deprotonation of ketimines/aldimines, then a migratory insertion process from metal-hydrides to 2-azadienes have been further developed. Of these processes, this thesis work will specifically focus on the …
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Clomeleon Biosensor-Mauslinien zur optophysiologischen Bestimmung der intrazellulären Chloridkonzentration in Nervenzellen
… bis auf 6 mM bei P20. Daraus folgt eine Umpolung der GABAergen Antwort bei P14. Darüberhinaus wurde eine universelle Clomeleon-Indikatormauslinie auf Basis des ubiquitär aktiven ROSA26-Promotors und einer loxP-flankierten Stopp-Kassette erzeugt. Durch Verpaarung mit einer …
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Intramolecular Anodic Olefin Coupling Reactions: Synthesis Of Nitrogen- And Oxygen-Heterocycles
… shown to be a powerful method for initiating umpolung reactions that allow the coupling of two nucleophilic functional groups. Most of the work in this area concentrates on making carbon-carbon bond. Hence, the reactions are usually terminated with olefin nucleophiles. The use of …
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Part 1. the mesomorphic properties of arloxy-s-triazines and their analogs, Part 2. the synthesis and polymerization behavior of α-aminonitriles and related compounds
… aminonitrile group after alkylation. Using this "umpolung”, or reversed polarity, approach we have demonstrated the utility of this class of compounds by reacting them with several activated aromatic dihalides and aliphatic dihalides to produce high molecular weight poly(bis-α-aminonitrile)s which …
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I. Development of three-component alkene carboamination reactions II. Palladium-catalyzed anti-Markovnikov oxidative amination of alkenes III. Chloroform as a carbon monoxide precursor: in or ex situ generation of co for pd-catalyzed carbonylations IV. Hydroalkylation of alkenes via photoredox catalysis
… of alkenes. The first leverages the umpolung tactic, using electrophilic amines and nucleophilic carbon components. An uncatalyzed mechanism involving radical intermediates was elucidated. The reaction displays poor chemoselectivity due to the formation of an oxyamination byproduct. …
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The Stetter reaction : synthesis of complex spiro Bis-indanes and studies on quaternary centre formation
This work covers recent advances in the Stetter reaction, including two novel domino Stetter reactions and preliminary studies on quaternary center formation via the intermolecular Stetter reaction. The N-heterocyclic carbene (NHC) catalyzed domino Stetter-aldol-Michael dimerization of o-formyl …
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Preparation of Novel Carbenes and their Catalytic Application to the Cross-Benzoin, Aza-Benzoin and Stetter Reactions
N-Heterocyclic carbenes (NHCs) derived from bicyclic triazolium salts possessing a fused 6 membered ring were found to induce chemoselectivity in the cross-benzoin between aromatic and aliphatic aldehydes. Use of these catalysts gave rise to predominantly one cross-benzoin product which could be …