by Ivan H.F. Chung. / Thesis (M.Phil.)--Chinese University of Hong Kong, 1995. / Includes bibliographical references (leaves 63-67). / Acknowledgements --- p.i / Contents --- p.ii / Abstract --- p.iv / Abbreviations --- p.v / Chapter Chapter I --- Introduction / Chapter I-1. --- General background --- p.1 / Chapter I-2. --- Asymmetric Diels-Alder reaction using chiral auxiliaries --- p.2 / Chapter I-2A --- Some well-known chiral auxiliaries --- p.3 / Chapter I-2B --- Carbohydrates as chiral auxiliaries --- p.6 / Chapter I-3. --- Asymmetric Diels-Alder reaction using chiral catalysts --- p.10 / Chapter Chapter II --- Results and Discussion --- p.14 / Chapter II-1. --- "Synthesis of η6-(benzyl 2-O-acryloyl-3,4-O-isopropylidene- β-L-arabinopyranoside) tricarbonylchromium(O) (47)" --- p.15 / Chapter II-2. --- "Syntheses of 4'-methylbenzyl 2-O-acryloyl-3,4-O- isopropylidene-β-L-arabinopyranoside (57) and η6-(4'- methylbenzyl 2-O-acryloyl-3,4-O-isopropylidene-β-L- arabinopyranoside) tricarbonylchromium(O) (56)" --- p.19 / Chapter II-3. --- "Syntheses of naphthylmethyl 2-O-acryloyl-3,4-O- isopropylidene-α-L-arabinopyranosides" --- p.22 / Chapter II-4. --- Diels-Alder reaction using the dienophiles 56 and 57 as the chiral auxiliaries --- p.25 / Chapter II-5. --- "Synthesis of benzyl 3,4-O-methylene-β-L-arabinopyranoside (81)" --- p.32 / Chapter II-6. --- Using the alcohol 81 as the ligand for Lewis acid in the Diels-Alder reaction --- p.36 / Chapter Chapter III --- Conclusions --- p.38 / Chapter Chapter IV --- Experimental Section --- p.40 / Chapter IV-1. --- Experimental section for the asymmetric Diels-Alder reaction using the chiral auxiliaries --- p.41 / Chapter IV-2. --- Experimental section for the asymmetric Diels-Alder reaction using the chiral catalysts --- p.59 / References --- p.63 / List of spectra --- p.68

by So Mei Po. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2000. / Includes bibliographical references (leaves 105-111). / Abstracts in English and Chinese. / Title Page --- p.i / Table of Contents --- p.ii / List of Tables --- p.v / List of Figures --- p.vii / Abbreviations --- p.xi / Acknowledgements --- p.xii / Abstract --- p.xiii / Chapter CHAPTER ONE --- INTRODUCTION / Chapter 1.1 --- Chiral Recognition Detected by Mass Spectrometry --- p.1 / Chapter 1.2 --- Fast Atom Bombardment Mass Spectrometry --- p.7 / Chapter 1.2.1 --- Desorption/Ionization in FAB --- p.7 / Chapter 1.2.1.1 --- Matrix --- p.8 / Chapter 1.2.1.2 --- Atom/Ion Guns --- p.9 / Chapter 1.3 --- Matrix-Assisted Laser Desorption/Ionization Mass Spectrometry --- p.9 / Chapter 1.3.1 --- Development of Matrix-Assisted Laser Desorption/Ionization --- p.10 / Chapter 1.3.2 --- Matrix-Assisted Laser Desorption/Ionization --- p.11 / Chapter 1.3.2.1 --- The Matrix --- p.12 / Chapter 1.3.2.2 --- Mechanisms of Ion Formation --- p.12 / Chapter 1.3.2.2.1 --- Desorption --- p.13 / Chapter 1.3.2.2.2 --- Ionization --- p.13 / Chapter 1.4 --- Blackbody Infrared Radiative Dissociation (BIRD) --- p.14 / Chapter 1.4.1 --- Photodissociation --- p.15 / Chapter 1.4.2 --- Blackbody Infrared Radiative Dissociation --- p.15 / Chapter 1.5 --- Outline of the Present Work --- p.18 / Chapter CHAPTER TWO --- INSTRUMENTATION AND EXPERIMENTAL / Chapter 2.1 --- Time-of-flight Mass Spectrometry --- p.19 / Chapter 2.1.1 --- Delayed Extraction --- p.23 / Chapter 2.1.2 --- Instrumentation --- p.24 / Chapter 2.1.2.1 --- Laser System --- p.24 / Chapter 2.1.2.2 --- Ion Source --- p.26 / Chapter 2.1.2.3 --- Reflector --- p.27 / Chapter 2.1.2.4 --- Detector --- p.27 / Chapter 2.1.2.5 --- Data Acquisition and Computer Control --- p.27 / Chapter 2.2 --- Fourier Transform Ion cyclotron Resonance Mass Spectrometry --- p.28 / Chapter 2.2.1 --- Ion Source --- p.29 / Chapter 2.2.1.1 --- Fast Atom Bombardment Mass spectrometry (FABMS) --- p.29 / Chapter 2.2.2 --- Electrostatic Ion Focusing System --- p.31 / Chapter 2.2.3 --- ICR Analyzer Cell and Magnet --- p.34 / Chapter 2.2.4 --- Data Acquisition and Handling system --- p.38 / Chapter 2.3 --- Experimental --- p.38 / Chapter 2.3.1 --- Matrix-Assisted Laser Desorption/Ionization Mass Spectrometry --- p.38 / Chapter 2.3.1.1 --- Sample Preparation --- p.38 / Chapter 2.3.1.2 --- Mass Spectrometric Analysis --- p.39 / Chapter 2.3.2 --- Fast Atom Bombardment Mass Spectrometry --- p.39 / Chapter 2.3.2.1 --- Sample preparation --- p.39 / Chapter 2.3.2.2 --- Blackbody Infrared Radiative Dissociation --- p.39 / Chapter CHAPTER THREE --- HOST-GUEST COMPLEXES DETECTED BY MATRIX- ASSISTED LASER DESORPTION/IONIZATION MASS SPECTROMETRY / Chapter 3.1 --- Introduction --- p.42 / Chapter 3.2 --- Sample Preparation --- p.45 / Chapter 3.3 --- Results and Discussions --- p.49 / Chapter 3.3.1 --- Cyclodextrins - Cyclic Maltooligosaccharides --- p.49 / Chapter 3.3.2 --- Maltooligosaccharide --- p.55 / Chapter 3.4 --- Conclusions --- p.64 / Chapter CHAPTER FOUR --- DIFFERENTIATION OF ENANTIOMERS USING MALDI-TOF-MS / Chapter 4.1 --- Introduction --- p.65 / Chapter 4.2 --- Experimental --- p.67 / Chapter 4.2.1 --- MALDI-MS Studies --- p.67 / Chapter 4.2.2 --- Calculation --- p.68 / Chapter 4.3 --- Results and Discussions --- p.69 / Chapter 4.3.1 --- MALDI-MS Studies --- p.69 / Chapter 4.3.2 --- Calculations --- p.74 / Chapter 4.4 --- Conclusion --- p.81 / Chapter CHAPTER FIVE --- BLACKBODY INFRARED RADIATION DISSOCIATION (BIRD) OF DIASTEREOCOMPLEXES / Chapter 5.1 --- Introduction --- p.86 / Chapter 5.2 --- Experimental --- p.88 / Chapter 5.3 --- Result and Discussion --- p.89 / Chapter 5.3.1 --- BIRD of Amino-acid/Cyclodextrin complexes --- p.89 / Chapter 5.3.2 --- BIRD of Proton-bound Amino Acid Dimers and Amino Acid/dipeptide Dimers --- p.91 / Chapter 5.4 --- Conclusion --- p.102 / Chapter CHAPTER SIX --- CONCLUSIONS AND FURTHER WORKS / Chapter 6.1 --- Conclusions --- p.103 / Chapter 6.2 --- Further Works --- p.104 / REFERENCES --- p.105

Wei Chunmei. / "September 2000." / Thesis (Ph.D.)--Chinese University of Hong Kong, 2000. / Includes bibliographical references (p. 137-140). / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Mode of access: World Wide Web. / Abstracts in English and Chinese.

by Yeung Kwan Wing. / Thesis submitted in: 2002. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2003. / Includes bibliographical references (leaves 68-73). / Abstracts in English and Chinese. / Contents --- p.i / Acknowledgement --- p.ii / Abstract --- p.iii / Abbreviation --- p.v / Chapter 1. --- Introduction --- p.1 / Chapter 1-1 --- Background --- p.1 / Chapter 1-2 --- Sharpless Epoxidation --- p.2 / Chapter 1-3 --- Mn-Salen Complexes for Epoxidation --- p.4 / Chapter 1-4 --- Oxaziridinium Salts --- p.6 / Chapter 1-5 --- Dioxiranes --- p.7 / Chapter 1-6 --- Asymmetric Epoxidation by Dioxirane --- p.11 / Chapter 2. --- Results and Discussion --- p.28 / Chapter 2-1 --- C-Glycoside Ulose Catalyst derived from L-arabinose --- p.28 / Chapter 2-2 --- Dioxirane epoxidation catalyzed by L-arabino-4-uloses --- p.30 / Chapter 3. --- Experimental Section --- p.51 / Chapter 4. --- References --- p.68 / Chapter 5. --- Appendix --- p.74

Orientador: Vicente Pleitez / Doutor

No description available.

Depuis des dizaines d’années, les chimistes organiciens ont accru leurs capacités à synthétiser des molécules complexes de manière exponentielle par le développement de nouvelles méthodes toujours plus élaborées. Malgré ces accomplissements, le challenge de synthétiser de nouvelles molécules toujours plus complexes de manière sélective et efficace reste toujours d’actualité. Dans le premier chapitre, nous introduirons la notion de chiralité de manière générale. Ensuite, les différentes stratégies pour contrôler la chiralité en synthèse organique seront exposées, en se focalisant plus particulièrement sur l’organocatalyse énantiosélective. Ensuite, dans le deuxième et troisième chapitre, le contrôle de la chiralité centrale sera étudié d’une part dans une synthèse de tetrahydropyranes et d’autre part dans l’addition de Michael impliquant les 1,3-cetoamides α,β-insaturés. Dans le quatrième chapitre, d’autres types de chiralité moins conventionnelles seront examinées. Tout d’abord, une étude portant sur la racemization des furanes atropisomères sera menée. Ensuite, des stratégie innovantes seront mises en œuvre pour la synthèse [4]- et [5] helicènes via notamment des phénomènes de conversion de chiralité. / In the last century, the ability of organic chemists to build complex molecules has grown exponentially. Despite these achievements, the challenge of synthesizing new molecules efficiently and selectively remains open. In the first chapter, we will discuss the definition of chirality as a transversal topic in science. Subsequently we will discuss the different strategies to control chirality in organic synthesis, with a special attention to organocatalysis. In the second and third chapter we will focus on the attempt to control central chirality for the synthesis of substituted tetrahydropyrans and the investigation of the reactivity of α,β-unsaturated 1,3-ketoamides in Michael addition. In the fourth chapter, other less conventional types of chirality will be examined. First, a study on the racemization of atropisomer furans will be conducted. Then, innovative strategies will be implemented for the synthesis [4] - and [5] helicenes via, in particular, chirality conversion approaches.

This thesis reports on the feasibility of the utilization of organotin hydrides as enaantioselective free radical reducing agents. The chiral organotin hydrides prepared contain the bulky chiral (1R,2S,5R)-menthyl substituent and in some cases also contain a stereogenic tin centre. Reaction of (1R,2S,5R)-menthylmagnesium chloride (MenMgC1) with triphenyltin chloride in THF proceeds with epimerization of the C-1 carbon of the menthyl group and results in a mixture of (1R,2S,5R)-menthyltriphenyltin and (1S,2S.5R)-menthyltriphenyltin. Addition of Lewis bases such as triphenylphosphine to the THF solution of triphenyltin chloride prior to the addition of the Grignard reagent suppresses epimerization and enables isolation of pure (1R,2S,5R)-menthyltriphenyltin. (1R,2S,5R)-Menthyltriphenyltin is the precursor for the synthesis of (1R,2S,5R)-menthyldiphenyltin hydride as well as (1R,2S,5R)-menthyl-containing organotin halide derivatives. A crystal structure of (1R,2S,5R)-menthylphenyltin dibromide and (1R,2S,5R)-menthylphenyltin dichloride confirmed the configuration of the menthyl substituent in these compounds. Reaction of MenMgC1 with diphenyltin dichloride in THF proceeds with no epimerization of the C-1 carbon of the menthyl group and bis((1R,2S,5R)-menthyl)diphenyltin is formed. A crystal structure of (1R,2S,5R)-menthyltriphenyltin confirmed the configuration of the menthyl substituent. Bis((1R,2S,5R)-menthyl)diphenyltin is used to form bis((1R,2S,5R)-menthyl)phenyltin hydride as well as other bis(1R,2S,5R)-menthyl derivatives. A series of chiral non-racemic triorganotin halides and triorganotin hydrides containing one or two (1R,2S,5R)-menthyl substituents as well as various potentially intramolecular coordination substituents were synthesized and characterized. The intramolecular substituents include the 8-(dimethylamino)naphthyl, 2-[(1S)-1-dimethylaminoethyl]phenyl, 2-(4,4-dimethyl-2-oxazoline)-5-methylphenyl and the 2-(4-(S)isopropyl-2-oxazoline)-5-methylphenyl substituents. Each compound containing a stereogenic tin centre was synthesized as diastereomeric mixtures. AM1 calculations of these compounds provide good qualitative predictability of the molecular geometries observed in the solid state as well as the diastereomeric ratios observed in solution. X-ray analysis of some of the organotin halides containing intramolecular coordination substituents revealed a tendency towards penta-coordination at the tin centre as a result of N-Sn interactions. The chiral organotin hydrides synthesized were found to be poor enantioselective free radical reducing agents. However, the addition of one molar equivalent of achiral or chiral Lewis acids to the free radical reduction reactions involving these organotin hydrides results in remarkable increases in enantioselectivity. There are numerous examples in which enantioselectivities exceed 80% and three examples of enantioselectivites which are equal and above 90% with one outstanding enantioselective outcome of ≥99%. These results appear to be the highest enantioselectivites for organotin hydride radical reductions reported to date. There is strong evidence to suggest that the chiral menthyl group of the organotin hydride directs the stereochemical outcome in the reduced product. The results also suggest that an increase in the number of menthyl substituents attached to tin or the introduction of intramolecular coordination substituents does not necessarily results in a greater increase in enantioselectivity. Preliminary studies into the synthesis of organotin hydrides containing Lewis acid functionalities are also reported. A zirconium chloride functionality was found to be incompatible with organotin hydride. However, an organotin hydride containing a trialkylboron Lewis acid functionality attached via an alkyl chain was successfully synthesized. Although this reagent was only stable in the preparative THF solution, it was still found to be effective at reducing benzaldehyde to benzyl alcohol.

Hydrogen bonding interactions have been applied to the synthesis of chiral vicinal diamines and the generation of helical chirality. A stereospecific synthesis of vicinal diamines was developed by using the diaza-Cope rearrangement reaction driven by resonance-assisted hydrogen bonds (RAHBs). This process for making a wide variety of chiral diamines requires only a single starting chiral diamine, 1,2-bis(2-hydroxyphenyl)-1,2-diaminoethane (HPEN) and aldehydes. Experimental and computational studies reveal that this process provides one of the simplest and most versatile approaches to preparing chiral vicinal diamines including not only C2 symmetric diaryl and dialkyl diamines but also unsymmetrical alkyl-aryl and aryl-aryl diamines with excellent yields and enantiopurities. Weak forces affecting kinetics and thermodynamics of the diaza-Cope rearrangement were systematically studied by combining experimental and computational approaches. These forces include hydrogen bonding effects, electronic effects, steric effects, and oxyanion effects. As an example of tuning diamine catalysts, a vicinal diamine-catalyzed synthesis of warfarin is described. Detailed mechanistic studies lead to a new mechanism involving diimine intermediates. Decreasing the NCCN dihedral angle by varying the diamine structure results in an increase of the enantioselectivity up to 92% ee. Hydrogen bonds have been used to generate helical chirality in a highly stereospecific manner with a single amino acid and 2,2′-dihydroxybenzophenone. DFT computational and experimental data including circular dichroism (CD), X-ray crystallography and 1H NMR data provide insight into the origin of the stereospecificity. A signalling dizao group can be attached to the receptor for general sensing of amino acid enantiopurity.

Hydrogen bonding interactions have been applied to the synthesis of chiral vicinal diamines and the generation of helical chirality. A stereospecific synthesis of vicinal diamines was developed by using the diaza-Cope rearrangement reaction driven by resonance-assisted hydrogen bonds (RAHBs). This process for making a wide variety of chiral diamines requires only a single starting chiral diamine, 1,2-bis(2-hydroxyphenyl)-1,2-diaminoethane (HPEN) and aldehydes. Experimental and computational studies reveal that this process provides one of the simplest and most versatile approaches to preparing chiral vicinal diamines including not only C2 symmetric diaryl and dialkyl diamines but also unsymmetrical alkyl-aryl and aryl-aryl diamines with excellent yields and enantiopurities. Weak forces affecting kinetics and thermodynamics of the diaza-Cope rearrangement were systematically studied by combining experimental and computational approaches. These forces include hydrogen bonding effects, electronic effects, steric effects, and oxyanion effects. As an example of tuning diamine catalysts, a vicinal diamine-catalyzed synthesis of warfarin is described. Detailed mechanistic studies lead to a new mechanism involving diimine intermediates. Decreasing the NCCN dihedral angle by varying the diamine structure results in an increase of the enantioselectivity up to 92% ee. Hydrogen bonds have been used to generate helical chirality in a highly stereospecific manner with a single amino acid and 2,2′-dihydroxybenzophenone. DFT computational and experimental data including circular dichroism (CD), X-ray crystallography and 1H NMR data provide insight into the origin of the stereospecificity. A signalling dizao group can be attached to the receptor for general sensing of amino acid enantiopurity.