This thesis contains the preparation of a new design of ligand for the palladium catalysed allylic substitution reaction. The phosphine oxazoline ligands detailed in the thesis give high levels of enantiocontrol when used in conjunction with symmetrical allyl systems in the palladium catalysed allylic substitution reaction. For unsymmetrical allyl systems the palladium catalysed allylic substitution process proceeds with complete regiocontrol and high levels of stereocontrol are again observed. The products from the palladium catalysed allylic substitution reaction can be readily converted to succinic acids, γ-lactones and aryl propanoic acids.

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.

<p> Extremal problems for asymmetric graphs and asymmetries of graphs are jointly investigated using function A(p,q). Values 0,1 of function are characterized.</p> / Thesis / Master of Science (MSc)

No description available.

No description available.

De nouveaux β-aminoalcools chiraux ont été synthétisés en 3 à 4 étapes avec de bons rendements globaux (19-42%). Ils ont été testés en tant que ligands dans la réaction de réduction de cétones aromatiques par transfert d’hydrogène. Des excès énantiomériques jusqu’à 91% ont été obtenus avec de bonnes conversions jusqu’à 99%. La réduction asymétrique de cétones aromatique par le borane a été également étudiée. Ces β-aminoalcools se sont montrés actifs mais pas très énantiosélectifs. Ces composés ont également été utilisés en tant que ligands dans la réaction d’addition du diéthylzinc sur des aldéhydes aromatique conduisant aux produits désirés avec de bons rendements (jusqu’à 98%) et de bonnes énantiosélectivités (jusqu’à 80%). En revanche, la réaction d’addition d’autres organométalliques (l’organozincique, le silane, l’étain et le nickel) sur aldéhydes montre de faible énantiosélectivité dans la plupart de cas.Dans la dernière partie de ce travail, un des β-aminoalcools synthétisés a été évalué dans la réaction de cyanation catalytique énantiosélective d’aldimines. Malgré des bonnes conversions obtenues, des faible énantiosélectivités ont été observées. / Chiral β-aminoalcohol compounds were prepared in 3 or 4 steps from isosorbide in good overall yields (19-42%). These compounds were used as ligands in the asymmetric transfer hydrogenation of aromatic ketones giving good enantioselectivities (up to 91% ee) and excellent conversions (up to 99%). The asymmetric reduction of aromatic ketones by borane complexes using these aminoalcohols was also evaluated. Good catalytic activity but low enantioselectivity were observed. Asymmetric addition of diethylzinc to aromatic aldehydes using these β-aminoalcohols was also studied leading to desired products in good yields (up to 98%) and good enantioselectivities (up to 80%). However, no asymmetric induction was observed when using other organometallics (organozinc, silane, nickel, tin).The last part of this work consisted in evaluating one of these β-aminoalcohols in the Titanium-catalyzed asymmetric cyanation of aldimines. Despite good conversions, low enantioselectivities were observed.

Recent years have seen a significant growth in what designers and players call asymmetric virtual reality (AVR) games. This dissertation creates a framework that defines the relevant characteristics of AVR as a genre and describes five common genres of AVR games, including David(s) and Goliath, Hide and Seek, Perspective Puzzle, Order Simulation, and Lifeline. The core features of each subgenre are expounded. These subgenres are then evaluated using design workshops to observe novice game designs use these subgenres in their game design process. An analysis of the workshops found that the AVR subgenre framework may benefit novice game designers in finding inspiration from patterns in existing AVR games, planning asymmetric mechanics in AVR games between VR and non-VR players, and concepting new and unexplored ideas within the AVR genre. Finally, the discussion section outlines similarities and differences in the subgenres, limitations in this research, and provides guidance for future directions for this research.

Obtaining enantiomerically pure compounds is of major importance in modern organic chemistry, and this PhD thesis outlines new advances made in this area. Two new enantioselective synthetic methodologies have been designed using isothiourea based- organocatalysts. A brief introduction to the recent literature involving this catalyst architecture is presented. Then, the results of the structure-activity relationship study carried out on a range of isothiourea catalysts for the kinetic resolution of (±)-1-naphthylethanol 16 is described. Chiral isothiourea HBTM 2.1 58 was identified as the optimum catalyst and was further employed in the resolution of a range of secondary alcohols. Good levels of conversion (c~50%) and selectivity (S up to 100) were achieved delivering alcohols in high levels of enantioselectivity (up to 98% ee). The synthetic utility of this process was subsequently demonstrated through isolation of a range of enantiopure alcohols (>99% ee) on a preparative scale, using low catalyst loading of HBTM 2.1 (0.10 mol%). Secondly, a new organocatalytic asymmetric transformation involving the generation of a C1-ammonium enolate using isothiourea is described. An intramolecular Michael addition-lactonisation (IMAL) of enone-acid substrates was developed using (‒)-tetramisole 37 as a catalyst. The generality of this protocol was probed via structural variation of the enone-acid substrates, providing a range of highly functionalised syn-polycyclic carbo- and heterocycles in excellent yields, diastereo- and enantioselectivities (up to 99% yield, 99 : 1 dr and 99% ee). Whilst investigating this process, we discovered that using cinchona alkaloid derivatives as catalysts gave preferential access to the diastereomeric anti-products. Therefore, a range of anti-dihydrobenzofurans was synthesised from readily available starting materials in good yield and stereoselectivities (up to 73%, 20 : 80 dr and 99% ee) using OTMS-quinidine catalyst. These two complementary synthetic strategies allowed facile and controllable access to both syn- and anti-diasteroisomers of a product in high enantioselectivity via judicious choice of catalyst. Subsequently, two telescoped procedures combining the synthesis of the enone-acid through olefination and asymmetric functionalisation were designed, giving rapid access to stereodefined pyrrolidines in high levels of diastereo- and enantioselectivitiy (up to 99 : 1 dr and 99% ee). The last part of this thesis describes preliminary studies toward the development of a doubly diastereoselective intramolecular Michael addition-lactonisation process, opening new avenues for the construction of complex molecular architectures.

published_or_final_version / Chemistry / Doctoral / Doctor of Philosophy

This paper investigates the influence of hedging on firm value and stock return exposures in U.S. oil and gas industry from 1998 to 2004. Previous empirical results show that the relationship between firm value and corporate hedging activities is mixed. We find that the trend and volatility of oil and gas prices play important roles in the issue. Our results indicate that corporate exposures to oil and gas prices are asymmetric. We also find that gas reserve hedging has significant impacts on firm value when volatility of gas price is high. In conclusion, our results show that corporate hedging policies may add firm values in some special situations.