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Showing 1 to 20 of 30 for “"Carbanion"”.
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Carbanion Accelerated Claisen Rearrangements
Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 1985.
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Synthetic Study Of Karlotoxins And Investigation Of Alpha-Diaminoboryl Carbanion Chemistry
… following the literature precedent. α-Boryl carbanion species are known to exhibit excellent olefinating abilities via boron-Wittig reaction. This type of reaction was first reported in the 1960’s, and actively studied mainly by Rathke, Pelter, and Matteson during the last third of the 20th …
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Phosphorus-Stabilized, Carbanion-Accelerated Claisen Rearrangements: Asymmetric Induction via 1,3,2-Oxazaphosphorinanes
The carbanion-accelerated Claisen rearrangement has been extended to include phosphorus carbanion-stabilizing groups. The appropriately substituted allyl vinyl ethers are synthesized by the nucleophilic addition of allyloxides to phosphorus-substituted allenes, which are obtained in one step from …
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I. Nuclear Magnetic Resonance Studies of Hyperconjugation. Ii. Quantitative Carbanion Studies
Made available in DSpace on 2014-12-09T17:35:29Z (GMT). No. of bitstreams: 1 6607800.pdf: 7353580 bytes, checksum: fd38630bf69a3380ff4b8fb88ef9a7bb (MD5) Previous issue date: 1966
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Reactions of 4-chloro-2,6-dimethoxypyrimidine and 2-chlorothiazole with carbanion nucleophiles
… of 4-chloro-2,6-dimethoxypyrimidine (1) with the carbanions of acetonitrile and propionitrile proceed exclusively by an ionic mechanism in liquid ammonia or THF to give a mixture of monosubstitution products resulting from displacement of chloride or the 6-methoxy substituent. With the …
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Beta-lithiations of carboxamides: An investigation of the regio- and stereoselectivity of directed lithiations
… $\beta$-metalation and of the structure of a carbanion of a $\beta$-phenyl tertiary amide has been carried out. The directed metalation has been found to occur with high diastereoselectivity and the resulting carbanion is best described as a pyramidal benzyllithium species based on $\sp{13}$C …
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Investigation of Substrate Specificity in Phosphate Binding Barrels and Mechanistic Studies of Orotidine Monophosphate Decarboxylase
… destabilization resolves the formation of a carbanion intermediate in a two-step mechanism: (1) the product isotope effect (PIE) is unity; (2) the proton at C6 of [6- 1H]-uridine 5'-monophosphate (h-UMP) exchanges to give [62H]-uridine 5'-monophosphate (d-UMP) in solvent deuterium and; (3) …
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A study of the displacement of halogen from chlorinated heteroaromatic azines by dialkali salts of benzoylacetone, disodio salts of certain 2-hydroxy-4-methylpyrimidines, and the methylsulfinyl carbanion
Halogenated monocyclic and bicyclic heteroaromatic azines, possessing a six or ten w-electron system and one or two ring nitrogens, have been shown to undergo nucleophilic displacement of halide ion with a variety of nucleophiles. A detailed review of the relative reactivity of compounds of these …
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Mechanistic and preparative studies of Electrochemical Deoxygenation and Debromination
… of the radical would be expected to form a carbanion. Protonation, presumably by trace water would give the observed alkane. Electrochemical deoxygenation of the benzylic vicinal diols was also observed. These generally resulted in elimination to form the alkene product. The more stable …
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Lithiation of Alkyl 2,6-Substituted Benzoates Adjacent to Oxygen: Alpha-Lithioalkyl Alcohol Synthons
… alcohol to generate a formal stable (alpha)-oxocarbanion is unknown. However, formation of an (alpha)-lithio alcohol derivative from an ester might be feasible because the formally bivalent oxygen has a partial positive charge which could provide dipole-stabilization of the formal adjacent …
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Studies on the use of alpha-silyl substituted carbanions in organic synthesis
… was studied using o(-trimethylsilylbenzyl carbanion and a series of N-aliphatic/aromatic azomethines. All reactions led stereoselectively to trans-olefins in moderate to low yields. The Peterson intermediate was isolated when neopentylideneaniline was used at room temperature. This …
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Photochemical, photophysical, and photobiological studies of zeolite guest-host complexes
… photodecarboxylation to generate a benzylic carbanion. The lifetime of the zeolite-encapsulated carbanion was found to be fifty times longer than in solution. The enhanced lifetime allows intermolecular nucleophilic addition chemistry to compete with protonation, effectively, a …
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Structural insights into conformationally-gated reactions catalyzed by thiamine pyrophosphate-dependent enzymes
… enzymes utilize TPP as a biological carbanion to initiate reactions on substrates with carbonyl carbon(s), such as pyruvate and 2-oxoglutarate, two central metabolites. This thesis presents structural analyses of three TPP-dependent enzymes. Most interestingly, each mechanism of three …
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A study of various nucleophiles in aromatic SRN1 reactions
… Upon 5-25 min of near-UV irradiation, the carbanions of 2-benzyl-4,4-dimethyl-2-oxazoline, ethyl phenylacetate, t-butyl acetate, N,N-dimethylacetamide and dimethyl methylphosphonate underwent reactions with both 2-bromopyridine and iodobenzene in an S<sub>R</sub><sub>N</sub>1 manner to give …
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The formation and chemistry of certain heterocyclic dianions
… and 4-chlorobenzyl chloride proceeded at the carbanion site. Aldol condensation of the dianion with benzophenone was accomplished, although similar reactions with several aromatic aldehydes failed. In addition to alkylation and aldol-type condensations, the disodio salt underwent Claisen-type …
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Kinetische Untersuchungen zur Nucleophilie stabilisierter Carbanionen
… 5. Die Kinetik der Additionsreaktionen der Carbanionen 24a-h mit den Chinonmethiden 20a-d wurde in Dimethylsulfoxid photometrisch verfolgt. Zusätzlich wurde eine Auswahl der Additionsprodukte isoliert und charakterisiert. In allen Fällen wurde ein Geschwindigkeitsgesetz 2. Ordnung für die …
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Development of novel methodologies utilizing quaternary ammonium salts as catalysts
… conjugate addition of sulfur-stabilized carbanion nucleophiles to α,β-unsaturated ketones and esters. This reaction was achieved using a substoichiometric amount of TBAF, resulting in high yields on the desired 1,4-addition product. The addition of 1,3-dithianes was given particular focus …
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Transition metal complexes of bis(diphenylphosphino)methane, dithizone and dithiolenes: structural, spectroscopic, electrochemical and computational studies
… were prepared by the metallation of the carbanion derived from [M(CO)₄(dppm)] (M = Cr, Mo or W), [ML(dppm)] (L= dithiolene; M = Pd or Pt), or the cationic precursor, [Ru(Cp)(PPh3)(dppm)]PF₆. The complexes were characterized by ¹H and ³¹P NMR, IR and UV/Vis spectroscopies and X-ray …
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The reduction of organic halides and diazonium salts with sodium borohydride
… without its bonding electrons, thus leaving a carbanionic site on the aromatic ring. The carbanion is subsequently quenched by a proton from the water. This reaction has also been shown to be applicable to aromatic systems other than benzene. On-halogen type displacement by the hydride ion also …
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Novel nitrogen containing polymers via Reissert chemistry
… which involved the reaction of a masked carbonyl carbanion synthon with activated aromatic fluorides. Hitherto unknown poly(aryl ketone sulfone)s were synthesized when this chemistry was extended with the use of bis(α-aryl aminonitrile)s. A novel quinodimethane was synthesized in quantitative …
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