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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
41

Applications of asymmetric allylation reactions towards natural product synthesis

Harsh, Philip R. January 2008 (has links)
Thesis (M.S.)--West Virginia University, 2008. / Title from document title page. Document formatted into pages; contains vi, 78 p. : ill. Includes abstract. Includes bibliographical references (p. 37-38).
42

New synthetic uses for chiral 1,3-dioxolan-4-ones /

Power, Lynn A. January 2008 (has links)
Thesis (Ph.D.) - University of St Andrews, May 2008.
43

Asymmetric dihydroxylation and aziridination of allenes and related chemestry /

Liu, Renmao, January 2007 (has links) (PDF)
Thesis (Ph. D.)--Brigham Young University. Dept. of Chemistry and Biochemistry, 2007. / Includes bibliographical references.
44

Design and evaluation of a new Lewis acid-assisted Lewis acid catalyst system and further applications of a double-allylation reagent

Sivasubramaniam, Umakanthan. January 2009 (has links)
Thesis (M. Sc.)--University of Alberta, 2009. / Title from PDF file main screen (viewed on Oct. 19, 2009). "A thesis submitted to the Faculty of Graduate Studies and Research in partial fulfillment of the requirements for the degree of Master of Science, Department of Chemistry, University of Alberta." Includes bibliographical references.
45

Amine promoted asymmetric cascade synthesis of highly functionalized heterocycles

Zhong, Cheng, January 2010 (has links)
Thesis (Ph. D.)--West Virginia University, 2010. / Title from document title page. Document formatted into pages; contains xvi, 498 p. : ill. (some col.). Includes abstract. Includes bibliographical references (p. 75-82).
46

New chiral bis(oxazoline) ligands for asymmetric catalysis

Le, Cong-Dung Thi, Pagenkopf, Brian L., January 2005 (has links) (PDF)
Thesis (Ph. D.)--University of Texas at Austin, 2005. / Supervisor: Brian L. Pagenkopf. Vita. Includes bibliographical references.
47

Electrophilic trapping of enolates in tandem reaction processes and (1,3-diketonato)metal templates for asymmetric catalysis

Bocknack, Brian Matthew, Krische, Michael J., January 2004 (has links) (PDF)
Thesis (Ph. D.)--University of Texas at Austin, 2004. / Supervisor: Michael J. Krische. Vita. Includes bibliographical references.
48

Asymmetric synthesis of (+)-L-alpha-(2'Z-fluoro)vinyllysine and its evaluation as inhibitor of lysine decarboxylase

Salud-Bea, Roberto de la. January 1900 (has links)
Thesis (Ph.D.)--University of Nebraska-Lincoln, 2006. / Title from title screen (site viewed May 23, 2007). PDF text: 231 p. : ill. ; 7.97Mb UMI publication number: AAT 3237598. Includes bibliographical references. Also available in microfilm and microfiche formats.
49

Asymmetric α-alkylation reactions / Asymmetric [alpha]-alkylation reactions

Klein, Rosalyn January 2000 (has links)
A novel camphor-derived hydroxy ketal 138 has been developed as a crural auxiliary, and used to prepare a series of six carboxylic esters of increasing steric bulk. The α-benzylation of this series of esters was achieved with diastereoselectivities of 59 - 83% d. e. and in 39 - 48% material yield. These results compared very favourably with those obtained in earlier studies using a regioisomeric analogue as the chiral auxiliary. Computer.modelling studies of the putative enolate intermediate has provided some insight into the possible mode of electrophilic attack at the α-carbon and the roles of the ketal protecting group and the lithium cation in these asymmetric transformations. In a related investigation, based on earlier work, a camphor-derived imino lactone has provided convenient access to α-alkyl α-amino acids, the imino lactone serving as a masked glycine equivalent. Using straight chain primary alkyl iodides [RI; R = Me, Et, Pr, Bu, CH₃(CH₂)₄ and CH₃(CH₄)₅], alkylation of the potassium enolate of the camphor-derived imino lactone was effected with 54 - 89% d.e. and in 54 - 87% material yield. Four novel alkylated derivatives were synthesised using isopropyl iodide, sec-butyl iodide and allyl iodide, the latter reagent resulting in both the monoallylated and diallylated products. While very good diastereoselectivities were achieved (83 - 88% d. e.) in these reactions, the material yields from reaction with the secondary alkyl iodides were low (31- 35%) due, presumably, to their decreased electrophilicity. Computer modelling studies of the enolate were carried out and support the hypothesis of endo attack by the electrophile on the enolate intermediate. These studies also indicate the possibility of coordination of the postassium cation to the endocyclic ester oxygen, thus effectively anchoring the bulky cation away from the reaction site.
50

Tetrol and derivatives: synthesis, host-guest properties and racemate resolutions

Pohl, Pieter Lourens January 2015 (has links)
In this study, we investigated the potential of a novel chiral host compound (+)-(2R,3R)-1,1,4,4-tetraphenylbutane-1,2,3,4-tetraol (TETROL) and its derivatives for use in racemate resolution using host-guest chemistry. The parent TETROL molecule is composed of a butane chain bearing a hydroxy functionality on each carbon, and two phenyl rings on each of the terminal carbons. The two internal carbon atoms are chiral. The syntheses of TETROL and derivatives were carried out by modifying the diester of naturally-occurring optically active tartaric acid using a variety of aromatic Grignard reagents. These included phenyl, anisyl, tolyl and naphthyl groups, as well as aromatic rings bearing fluoro and trifluoromethyl substitutents. The substituents on the aromatic rings were located in the ortho, meta or para positions. The so-obtained potential host compounds were investigated for their inclusion abilities by recrystallizing them from a number of potential chiral guest compounds such as 2- and 3-methylcyclohexanone, camphor, i-propanol and 2-butanol, as well as various achiral organic compounds. Host:guest ratios were determined by means of 1H-NMR spectroscopy. Of the hosts investigated, TETROL appeared to favour a host:guest ratio of 1:1 for all included compounds. It complexed with cyclic ketones such as cyclohexanone and derivatives, and also cyclic alcohols and amines like cyclohexanol and morpholine. TETROL, however, was not able to include short chain or branched chain alcohols such as i-propanol and 2-butanol. p-AnisylTETROL showed similar inclusion abilities to TETROL but, in addition, enclathrated i-propanol and 2-butanol. p-TolylTETROL showed a preference for the inclusion of alcohols over ketones. In general, the ortho-substituted aromatic derivatives of TETROL faired relatively poorly as hosts, with some exceptions. Of the hosts investigated, TETROL appeared to favour a host:guest ratio of 1:1 for all included compounds. It complexed with cyclic ketones such as cyclohexanone and derivatives, and also cyclic alcohols and amines like cyclohexanol and morpholine. TETROL, however, was not able to include short chain or branched chain alcohols such as i-propanol and 2-butanol. p-AnisylTETROL showed similar inclusion abilities to TETROL but, in addition, enclathrated i-propanol and 2-butanol. p-TolylTETROL showed a preference for the inclusion of alcohols over ketones. In general, the ortho-substituted aromatic derivatives of TETROL faired relatively poorly as hosts, with some exceptions. X-Ray data of the inclusion complexes indicated that a pair of 1,3-intramolecular hydrogen bonds was a significant stabilizing factor of the geometries of all the hosts. The guest was always held in the host crystal by means of a hydrogen bond with the host, where the host functioned as the hydrogen bond donor and the guest as the acceptor. There were a number of other inter- and intra-molecular contacts that further stabilized the inclusion complexes. A surprising feature of the inclusion of 3-methylcyclohexanone, as elucidated by X-ray analysis, was that its methyl group adopted the axial orientation, the higher energy conformation for these kinds of molecules, and a 3-alkylketone effect was proposed to be one of the reasons for this observation. Thermal data was used to assess the relative thermal stabilities of the complexes, and the results compared with features of the X-ray structures, in order to determine whether thermal stability is related in some way to the nature of the guest packing in the host crystal. the case of the racemic guests, complexes obtained were analysed using chiral GC-MS. TETROL preferred the R-enantiomers of 2- and 3-methylcyclohexanone (21.7% and 16.7% e.e.). The S-enantiomer of camphor was favoured but the e.e. was low (3.8%). p-AnisylTETROL had a preference for the S-enantiomer in the case of 2- and 3-methylcyclohexanone as well as 2-butanol (44.3%, 20.4% and 1.7% e.e., respectively). p-TolylTETROL could only successfully resolve 2-butanol (23.5% e.e. in favour of the R-enantiomer). o-TolylTETROL preferred the R-enantiomers of methyl phenyl sulfoxide (29.2% e.e.) and 2-butanol (21.5% e.e.). Overall, TETROL and its derivatives exhibited the ability to resolve racemic mixtures to some extent.

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