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Showing 1 to 20 of 115 for “"lithiation"”.
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Studies on directed lithiation: 1. Reactivity studies on alkoxide-directed lithiation reactions. 2. NMR spectroscopic characterization of the solution structure of an asymmetric lithiation reagent
… of organolithium aggregates is described. The lithiation of the cyclopropyl rings of a rigid bis-cyclopropylcarbinol has been shown to occur via two sequential lithiation steps. The first lithiation occurs very rapidly compared to the lithiation of other cyclopropane rings and appears to be the …
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The Ortho Lithiation of Tertiary Benzamides
… yields of 21-87%. A mechanistic study indicated lithiation of the ortho position is direct rather than the result of rearrangement of an initially formed (alpha)-aza anion.
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Beta'-Lithiation of Alpha, Beta-Unsaturated Amides
The novel (beta)'-lithiation of (alpha)-alkyl-(alpha),(beta)-unsaturated secondary and tertiary amides is reported. N-Methyl-1-cyclohexenecarboxamide and N-methyl-1-cyclopentenecarboxamide are metalated at nitrogen and at the (beta)'-carbon with either sec-butyllithium/TMEDA at -78(DEGREES)C or …
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New lithiation methodologies to 2-substituted nitrogen heterocycles
… describes the development of methodologies for lithiation-trapping and lithiation-arylation of N-Boc heterocycles in the position α to nitrogen as well as in situ infra-red spectroscopic monitoring of lithiation reactions and the application of lithiation-arylation in total synthesis. Chapter 2 …
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Enantioselective lateral lithiation-substitution reactions using benzamide directing groups
Reactions involving organolithium reagents under the influence of the chiral ligand to affect the enantioselective replacement of a carbon-proton bond with a carbon-carbon bond or a carbon-heteroatom bond are described.
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Kinetics and Mechanism of Syn, Alpha' Lithiation of Tertiary Benzamides
The reaction of N,N-dialkyl-2,4,6-triisopropylbenzamides with sec-butyllithium in cyclohexane yields a product in which metalation has occurred exclusively at the carbon adjacent to nitrogen and syn to the carbonyl group. Evidence obtained by nuclear magnetic reso- nance, freezing point depression …
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Enantioselective Alpha-Lithiation of N-Boc-N-(p-Methoxyphenyl)allylamines Mediated by (--)-Sparteine
Tin-lithium exchange of enantioenriched allylic stannanes in the presence of (-)-sparteine followed by electrophilic substitution provides enecarbamates with configurations opposite to that obtained by the deprotonation sequence. The enecarbamates can be hydrolyzed to aldehydes or reduced to …
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Asymmetric Lithiation-Substitution Sequences of Functionalized Allylic and Benzylic Amines Mediated by (-)-Sparteine
Modification of the allyl amine with selected substituents at the beta and gamma-positions allowed for an examination of yields, product distributions, enantioenrichments, mechanistic understanding and synthetic applications. With an extended allyl amine, enantioenriched diene products were …
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Lithiation of Alkyl 2,6-Substituted Benzoates Adjacent to Oxygen: Alpha-Lithioalkyl Alcohol Synthons
The removal of an sp('3) proton alpha to the bivalent oxygen of an ether or 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 …
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Structural evolution of α-Fe2O3 nanowires during lithiation/delithiation and electrochemical property improvement
… the anode material at various stages of lithiation and delithiation. The phase and morphological evolution demonstrate the conversion reaction process in α-Fe2O3. The process was initiated through the reduction of Fe2O3 to Fe3O4 nanocrystals, which form 4-nm-nanoparticles within the …
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Lithiation-induced phase transitions in alloying anodes for thin film lithium-ion batteries
… This thesis explores different types of lithiation-induced phase transitions and develops corresponding kinetic models in amorphous Si and Ge films using a framework consisting of electrochemical, structural and analytic approaches. The first section of this thesis covers the initial …
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Electrochemical lithiation and delithiation for control of magnetic properties of nanoscale transition metal oxides
… solid state chemical synthesis or via chemical lithiation. In this work, changes in magnetization and structure of pulsed laser deposition (PLD)-grown Fey's (magnetite) thin films, Fe3O4 nanoparticles, and CrO2 nanoparticles have been investigated upon electrochemical lithiation. The reasonable …
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Mechanistic Investigations and Synthetic Development of (-)-Sparteine Mediated Asymmetric Benzylic Lithiation-Substitution Reactions of Secondary Amides
The synthetic utility of the lithiation-substitutions of N-(2-phenethyl)isobutyramide has also been investigated. Enantioenriched substituted products have been carried forward in the synthesis of 1,4-disubstituted dihydro- and tetrahydroisoquinolines. Variation of either substituent is convenient …
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Intermolecular and intramolecular asymmetric induction at the beta-benzylic position of carboxamides in directed lithiation-substitution sequences
… position of secondary carboxamides in directed lithiation-substitution reactions has been achieved intermolecularly by using ($-$)-sparteine as the external chiral ligand and intramolecularly by using $\alpha$-methylbenzylamine as the covalently attached chiral auxiliary.
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Lithiation of Oxy-Arenes; New Methodology for Electrophilic Aromatic Substitutions: Attempted Synthesis of Thiaheptalenes and Heterocyclic Pyrene Systems
Lithiation of oxy-arenes was studied. The lithiation of 4-hydroxyphenanthrene with 2 eq. of n-butyllithium/TMEDA in cyclohexane at 23(DEGREES)C occurs completely at the 5-position, although the 5-position is the most hindered position in the 4-hydroxyphenanthrene. By contrast, the lithiation of …
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The directed ortho-lithiation of lithium phenylsulfide and lithium phenylselenide plus sigma-aromaticity and the hexakis(phenylseleno)benzene dication
The directed ortho-lithiation of lithium phenylselenide by reaction with $n$-butyllithium in cyclohexane with $N$,$N$,$N\sp\prime$,$N\sp\prime$-tetramethylethylenediamine gives almost quantitative conversion to lithium 2-lithiobenzeneselenolate and is estimated to be seven to eight times faster …
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Enantioselective lateral lithiation-substitution of o-ethyl- and o-benzyl-N-pivaloylanilines: Studies of a pathway of stereoinformation transfer
The secondary amides o-ethyl-N-pivaloylaniline and o-benzyl-N-pivaloylaniline are laterally lithiated by sec-butyllithium to generate a dilithio intermediate. Electrophilic substitution of the organolithium in the presence of ($-$)-sparteine provides the products with enantiomeric excesses close to …
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I. Hexaiodobenzene Dication: A Ten-Electron Sigma-Delocalized Huckel-Aromatic Species. Ii. Synthesis and Study of Ortho-Bridged Triarylmethyl Compounds (Lithiation)
The synthesis of the bis trifluoromethanesulfonate salt of hexaiodobenzene dication is described. Experimental evidence supports the postulate that it is a ten-electron sigma-delocalized Huckel-aromatic species.
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Diastereoselective Lithiation-Substitution of N-Silyl-Protected-(S)-Tetrahydro-1H-pyrrolo[1,2-c]imidazole-3(2H)-ones and Applications of Their Derivatives
… group that undergoes diastereoselective lithiation followed by electrophile quench to give C5-substituted products with syn stereochemistry. The N-silylated derivatives may be more easily N-deprotected as compared to previous N-t-Bu analogues to give secondary ureas. These may serve as …
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Diastereoselective Lithiation-Substitution of N-Silyl-Protected-(S)-Tetrahydro-1H-pyrrolo[1,2-c]imidazole-3(2H)-ones and Applications of Their Derivatives
… group that undergoes diastereoselective lithiation followed by electrophile quench to give C5-substituted products with syn stereochemistry. The N-silylated derivatives may be more easily N-deprotected as compared to previous N-t-Bu analogues to give secondary ureas. These may serve as …
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