Thesis (Ph. D.)--University of Texas at Austin, 2005. / Supervisor: Stephen F. Martin. Vita. Includes bibliographical references.

Thesis (Ph. D.)--University of Texas at Austin, 2008. / Vita. Includes bibliographical references.

1. In the first part of this thesis, the concept of a tether based intramolecular crossed -acyloin reaction mediated by heterogeneous lithium/ 4,4' -di-teti-butylbiphenyl (Li/DBB) reducing conditions was examined. The objective of the project was to accomplish an intramolecular crossed-acyloin reaction, by employing non-symmetric di-esters, linked with a suitable tether (diol) between the two acyl functionalities. Chapter 1: Introduction - Acyloin Condensation. The concept of carbon-carbon coupling reactions between two carbonyl functionalities to synthesise a-hydroxyketone (acyloin) moieties is described. Generally, there are two methods, either by bimolecular reductive coupli ng of esters, known as acyloin condensation or the umpo/ung dimerisation of aldehydes, known as benzoin condensation. The background and recent developments in these reaction categori es are discussed in this section. In addition, this section outlines the project's aims and describes the previous work conducted in the group. Chapter 2: Results & Discussion - An Alternative Route to Crossed-ocyloin In this section, the tether based intramolecular crossed-acyloin reaction mediated by Li/DBB reducing conditions is introduced. This work is based on the hypothesis that a suitable tether, could promote an intramolecular crossed-acyloin reaction. The objective was successfully achieved through a series of competition experiments, which demonstrated that the application of exo-exo norbornenediol as a tether exclusively formed crossed-acyloin products. This discovery was accompanied by an investigation into regi oselective crossed-acyloin reaction. 2. In the second part of this thesis, the Sharpless Asymmetric Epoxidation (SAE) desymmetrisation reaction of O'-symmetric diene 1,3-diols was exami ned. It was suggested that formation of the epoxide would trigger a stereoselective 5-exo-tet ring closure to deliver predominately trans-THF adducts. Chapter 3: Introduction - Metal Mediated Synthetic Routes to trans-2,5-Disubstituted THFs This section introduces the transition metal mediated cyciisation of bishomoallylic alcohol, to the corresponding trans- THF moieties. In particular, the development and application of three methods were highlighted; rhenium mediated (3+2) oxidative cyclisation, cobalt catalysed oxidative cyclisation and an rc-allylpalladium complex catalysed reaction. In addition, the concept of the Sharpless Asymmetric Epoxidation (SAE) is introduced and the project objectives are outlined. Chapter 4: Results & Discussion - A NOJel Route Towards trans- THFs The primary effort was to design a robust route to form the test substrate, (3R,55}hepta-1,6-diene- 3,5-diol, which was accomplished in good yield by Ring Opening/Crossed metathesis (ROM) of silyl ether protected (1 R, 35 }cyclopent-4-ene-1,3-diol. The expe rimental results have demonstrated that SAE of the diene 1,3 diol formed trans-THF. Chapter 5: Experimental Full experimental procedures and characterisation of the synthesised molecules are reported.

Thesis (Ph. D.)--Ohio State University, 2004. / Title from first page of PDF file. Document formatted into pages; contains xviii, 228 p.; also includes graphics. Includes bibliographical references (p. 128-137).

Ionic liquids (ILs), consisting of ions that are liquid at ambient temperatures, can act as solvents for a broad spectrum of chemical processes. These ionic liquids are attracting increasing attention from industry because they promise significant environmental as well as product and process benefits. ILs were used as solvents for two industrially important homogeneous reactions namely metathesis of 1-octene and the hydroformylation of vinyl acetate. In the metathesis of 1-octene, several reaction parameters were investigated, including temperature, catalyst (type and concentration) and influence of ionic solvent and conventional solvents. Temperature and catalyst concentration were found to be rate-determining factors, but played smaller roles in determining the outcomes of the reactions compared to the influence of individual ILs. It was discovered that more polar ILs were favourable in producing high rates and selectivities. Imidazolium-based cations and tetrafluoroborate anions were superior in activity when compared to other combinations of cations and anions. The addition of catalyst promoters such as phenol and tin(II) chloride were also investigated and found to enhance metathesis rates in “neat” reactions. These catalyst promoters inhibited metathesis rates when used in combination with ILs. In the hydroformylation of vinyl acetate, several reaction parameters were investigated, including temperature, catalyst concentration, vinyl acetate concentration, ligand concentration, syngas pressure and influence of ionic solvent and conventional solvents. It was shown that high n : i ratios of aldehyde products were formed with specific IL systems. Also, low ligand concentrations and low vinyl acetate concentrations increased selectivities, although rates of reactions were somewhat compromised. Lower syngas pressure and lower temperatures afforded enhanced selectivities, again at the expense of reaction rates. Depending on whether fast reaction rates or high regioselectivity is required, the IL and general reaction conditions can be tailored to fit the needs of the reaction. It was discovered that aromatic-containing ammonium-based ILs v afforded high rates at low selectivity. Bulkier ammonium cations tended to give lower rates but the selectivity was significantly enhanced. Impurities present in ILs have also been shown to have a marked effect on hydroformylation rates and selectivity. The reader will be accompanied along a path designed to discover an optimised set of reaction conditions, the path of which will take the reader from reactions providing low selectivities, low turnover numbers and low yields to a much brighter picture, namely extremely high selectivities, turnover numbers and yields. / Prof. D.B.G. Williams

This thesis details progress towards the development of an organocatalytic carbonyl-olefin metathesis of norbornene. This transformation has not previously been done catalytically and has not been done in practical manner with stepwise or stoichiometric processes. Building on the previous work of the Lambert lab on the metathesis of cyclopropene and an aldehyde using a hydrazine catalyst, this work discusses efforts to expand to the less stained norbornene. Computational and experimental studies on the catalytic cycle are discussed, including detailed experimental work on how various factors affect the difficult cycloreversion step. The second portion of this thesis details the use of chiral cyclopropenimine bases as catalysts for asymmetric Michael reactions. The Lambert lab has previously developed chiral cyclopropenimine bases for glycine imine nucleophiles. The scope of these catalysts was expanded to include glycine imine derivatives in which the nitrogen atom was replaced with a carbon atom, and to include imines derived from other amino acids.

No description available.

This thesis describes a new catalytic activity of a commonly used metathesis catalyst and demonstrates the viability of directly coupling two powerful C-C bond forming strategies: cross-metathesis and ylide transformations, both proceeding via metal-catalysed carbene transfer. Catalytic C-C bond formation reactions are highly significant; my studies focus on such transformations involving metallocarbenes. Grubbs' 2^nd generation Ru catalyst is the most commonly used catalyst in olefin metathesis to generate thermodynamically preferred trans-olefms. During the course of my studies, I established that Grubbs 2^nd generation catalyst (0.5 mol%) can also dimerise diazoacetates to give cis-enediesters (maleates) in good to excellent yields (74-99%) with high stereoselectivity (Z:E>95:5). The reaction between two different diazoacetates, catalysed by Grubbs catalyst gave access to unsymmetrical cis-enediesters with high stereoselectivity (Z:E>95:5, generally 99:1). The catalyst was found to retain its alkene metathetical activity during diazo coupling; building on this latter observation a novel route to access dienyl dilactones by head-to-head dimerisation of unsaturated diazoacetates was developed. Cross-metathesis was found to be chemoselective in the presence of diazo functionality (when flanked by two carbonyl groups), allowing the functionalisation of tethered olefin. The elaborated diazocarbonyl olefms were subjected to Rh₂(OAc)₄ catalysed ylide formation and subsequent transformations. Significantly, one-pot cross-metathesis/ylide transformations (1,3-dipolar cycloaddition and [2,3]-simgatropic rearrangement) also proved to be viable, establishing that the spent Ru catalyst following metathesis does not affect the subsequent Rh(II)-catalysed transformation.

Thesis (Ph. D.)--University of Nevada, Reno, 2007. / "December, 2007." Includes bibliographical references. Online version available on the World Wide Web.

Thesis (M.S.)--University of Florida, 2004. / Title from title page of source document. Document formatted into pages; contains 50 pages. Includes vita. Includes bibliographical references.