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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.
51

Climate Change Adaptation and Flooding scenarios in the Baltic Sea : A comparative study of models of stakeholder involvement and public participation in Sweden and Demark

Ndip-Achere, Arrey Hansel January 2010 (has links)
One common idea within participation theory is the need for new approaches in decision making that emphasize a two-way interaction between decision makers and the public as well as deliberation among participants. Citizens should be given the opportunity to weigh evidence, discuss and debate potential decision options and possibly arrive at mutual agreements by which all parties can abide. The demand for sound scientific information and public participation is particularly great especially in adapting to some of the impacts of climate change such as floods due to sea level rise. The uncertainties and the socially sensitive nature of such risk, makes it important for all relevant stakeholders to be involved. This study draws on two research projects carried out in Sweden and Denmark with the intention of engaging stakeholders in finding suitable ways of adapting to climate change. The two cases that have been selected for this study include the SEAREG (Sea Level Change Affecting the Spatial Development in the Baltic Sea Region) and the BALTCICA (Climate Change: Impacts, Costs and Adaptation in the Baltic Sea Region). Using a comparative case study method, this thesis looks into the design of participatory processes and the conceptions that underlie them, as well as the consequences on the active participation of other stakeholders with a particular focus on the public. Some of the main differences on the extent of public participation between these projects are sorted out and compared using theoretical perspectives from participation theory. Both cases cut across the local and national scales of decision making and use flooding scenarios in communicating with the public. However, the design of these scenarios as well as the participatory models differ.
52

1. Synthetic Study of Pyrrolizidine Skeleton 2. Synthetic Study Toward Tylophorine and Cryptopleurine 3. Synthetic Study of Fused Bicyclic Glutarimides

Hsu, Ru-Ting 18 January 2005 (has links)
Reaction of 3-sulfonyl acetamides with various substituted methyl acrylate derivatives furnished pyroglutamate and glutarimidess via [3+2] and [3+3] cycloaddition respectively. The results were applied to the synthesis of pyrrolizidine skeleton, tylophorine, cryptopleurine and fused bicyclic glutarimides.
53

1. Synthesis of Nonlinear Optical Chromophores 2. New Approaches to Quinolone Skeleton

Tsai, Tsung-Hsiu 27 June 2005 (has links)
Chapter 1: Reaction of benzoaldehyde with wittig agents or isophone to build up conjugate carbon chain, then combined with electron acceptor to furnished the chromophores. The charge-transfer chromophores, which have the first molecular hyperpolarizability
54

Synthetic Studies Toward Xylopinine

Chang, Jung-Kai 18 August 2005 (has links)
We use stepwise [3+3] annulation to prepare the asymmetric glutarimides, and then establish a new approach to isoquinolone skeleton starting from glutarimides via regioselective nucleophilic addition and ring-closing metathesis reaction. Finally, we applied this method to the synthetic studies toward (¡Ó)-Xylopinine.
55

Synthesis Of Heteroaryl Substituted Dihydrofuran And Dihydropyran Derivatives By Green Chemistry Approach

Demirci, Sema 01 September 2009 (has links) (PDF)
The thesis subject is mainly involved in Green Chemistry approach. Thiophene, furan and pyridine carboxaldehydes were chosen as starting compounds and vinylation and allylation with Grignard reaction afforded the corresponding racemic heteroaryl substituted allylic and homoallylic alcohols. Subsequent resolution with enzymes (PS-Amano II, Lipozym and Novazym 435) gave enantiomerically enriched alcohols with the e.e. values varied between 65 and 99%. The absolute configurations of all substrates are known. As a result of O-allylation with the common procedure formed the feasible carbon backbone for the ring closing metathesis reaction. All ring closing metathesis reactions were performed by Grubbs&rsquo / catalyst with just 5% catalyst loading. The absolute configurations of dihydrofuran and dihydropyran derivatives are known, since the chiral center configurations of all substrates are preserved throughout all the applied processes.
56

Synthesis Of Chiral Diene Systems Via Ring Closing Enyne Metathesis And Their Applications In Diels-alder Reactions

Cayir, Merve 01 July 2010 (has links) (PDF)
The main subject of this thesis is synthesis of chiral diene systems via Ring Closing Enyne Metathesis (RCEM). Furan and thiophene carbaldehydes were chosen as starting compounds. As a result of allylation and propargylation reaction of these aldehydes targeting racemic heteroaryl substituted homoallylic and homopropargylic alcohols were synthesized. Enantiomerically enriched alcohols were obtained by enzymatic resolution method with different enzymes (PS-II, Lipozyme) with the high enantiomeric excess values. Absolute configurations of all alcohols are known. O-allylation and O-propargylation reactions of enantiomerically pure alcohols, afforded feasible enyne units for RCEM were synthesized successfully. All RCEM reactions were performed by using Grubbs&amp / #8223 / 1st generation catalyst. The absolute configuration of all chiral diene systems were known since during the course of the all reactions, configurations were preserved. As a last step, Diels-Alder reactions were applied to some of these chiral diene systems to get bicyclic compounds and comment on the stereoselectivity. Only one diastereomeric cycloadduct was observed as a result of Diels-Alder applications.
57

Chemoenzymatic Synthesis Of Enantiomerically Enriched Gamma And Delta Lactones

Sardan, Melis 01 September 2010 (has links) (PDF)
The major subject of this thesis is the synthesis of enantiomerically enriched gamma and delta lactones via Ring Closing Metathesis (RCM). Furan and thiophene substituted aldehydes were transformed to the corresponding heteroaryl substituted allylic and homoallylic alcohols by using vinyl and allylmagnesium bromide, respectively and then resultant racemic alcohols were resolved by hydrolase type enzymes (PSC-II, Lipozyme, CAL-B) with high enantiomeric excess values. Since the absolute configuration of alcohols were known, it was possible to determine the configuration of the synthesized compounds. After the enantiomeric enrichment of the alcohols, subsequent acylation with acryloyl and methacryloyl chloride afforded feasible diene system that was subjected to ring closing metathesis reaction 1st and 2nd generation Grubbs&rsquo / catalysts were used. These lactones were used to test their biological activities.
58

Functionalization of Resorcinarenes and Study of Antimicrobial Activity

Muppalla, Kirankirti 21 May 2001 (has links)
Cavitands are very important class of compounds in supramolecular chemistry. These molecules contain rigid enforced cavity,and have attracted considerable attention in supramolecular chemistry as building blocks for the construction of carcerands, hemicarcerands, and other host guests complexes. Nearly 40 years ago, Niederl and Vogel laid foundation for the study of such type of condensation reactions. In our laboratory we are involved in synthesis of resorcinarenes with readily available substrates such as resorcinol and aldehydes to form a cyclic tetramer. Herein, I present detailed studies about the functionalization of the synthesized tetramers and their antimicrobial activity. Octahydroxy resorcinarenes were synthesized and perallylated which served as acyclic diene precursors for ring closing metathesis reaction. Studies were carried out to see effect of C-2 substituent of resorcinol and effect of aryl substituents, and aliphatic substituents on ring closing metathesis. This thesis describes the synthesis of bridged resorcinarenes and study of antimicrobial activity of resorcinarenes.
59

Application of the Moore rearrangement to the synthesis of 1,4-dioxygenated xanthones and efforts toward the total synthesis of lundurine B

Nichols, Alexander Lindsey 31 January 2013 (has links)
A novel application of the Moore rearrangement was successfully developed and applied to the synthesis of 1,4-dioxygenated xanthones that would have been difficult to obtain otherwise. The 1,4-dioxygenated xanthone moiety is found in several naturally occurring, biologically active compounds. Several methods by which to obtain the 1,4-dioxygenated xanthone core have been reported; however, high step counts, low yields, and harsh reaction conditions preclude the use of these methods to complex xanthone natural products. Using the Moore rearrangement as a key step in the synthetic sequence has allowed us to prepare several xanthone natural products quickly and more efficiently than what is possible with the prior art. Using the Martin group’s prior experience with the application of ring closing metathesis (RCM) to the field of alkaloid natural product synthesis, the preparation of lundurine B was undertaken. Key features of the proposed synthesis to lundurine B include the formation of a cyclopropane ring by the formation pyrazoline intermediate via [3+2] dipolar cycloaddition followed by dinitrogen extrusion. A second key step in the proposed sequence to lundurine B is a double RCM to form a five- and eight-membered ring in a single operation. While double RCM strategies have been applied to several elegant natural product syntheses, the formation of a five- and eight-membered ring in a single sequence has not been reported. Should the double RCM strategy prove successful for lundurine B, the conditions could in principle be applied to other structurally related natural products. / text
60

A novel approach to manipulate cavity size In resorcinarenes

Parulekar, Sumedh 01 June 2006 (has links)
Intramolecular ring closing metathesis in the presence of Grubbs' catalyst has been used as an efficient approach to synthesize bridged resorcinarenes. Octaallyl cavitands may undergo conformational changes; however bridge formation by RCM of the allyl groups gives a rigid, enforced, concave cavity capable of holding neutral molecules. This is the first report describing tandem formation of the four bridges on the upper rim of resorcinarenes. Structures of bridged resorcinarenes are confirmed by spectral analysis data.This report also describes the synthesis of polyhydroxy resorcinarenes, which have been used as metal complexing agents, sensors, receptors, molecular reaction vessels and catalytic chambers. They are able to encapsulate small neutral molecules, drug molecules inside the cavity. Such cavitands offer unique molecular platforms for host--guest chemistries, as well as new polymers and self-assembled systems.

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