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Th. doct.-ing.--Sci. des matér.--Toulouse--I.N.P., 1983. N°: 263.

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

Thesis (PhD)--Stellenbosch University, 2003. / ENGLISH ABSTRACT: Please refer to full text for abstract / AFRIKAANSE OPSOMMING: Sien asb volteks vir opsomming

Different diphosphine ligands having the structure shown below have been studied for carbonylation and hydroformylation reactions. Depending on the substituent on the phosphorus atoms the electronic and steric properties can be tuned to direct the reaction towards the desired products. Palladium methoxycarbonylation of a large variety of unsaturated compounds has been attempted under very different conditions. The outcome of these reactions was the achievement of the linear products with a selectivity higher than 99.5 % under mild conditions of pressure and temperature. Chloroaromatic compounds have also been employed as substrates in methoxycarbonylation reactions. Unexpected results were observed since carbonylation was possible only when a strong electron withdrawing group was present. The origin of the many side products from these reactions has been elucidated. Rhodium hydroformylation was not as successful as palladium Methoxycarbonylation since relatively severe conditions had to be used to get good rates and good selectivity. In no case were there as good as those obtained in the carbonylation reactions. However, unusual factors, such as the presence of chlorine in the reaction media, have been found to influence either the conversion or the selectivity.

The hydroformylation of 1-octene with supported ionic liquid phase catalyst was demonstrated when using a system involving the substrate, reacting gases and products in CO₂ and N₂ flow over a fixed bed supported ionic liquid phase catalyst (silica gel and carbon aerogels as solid support respectively) at different system pressures. Yields, reaction rates, selectivities and rhodium leaching were all monitored. A pressure of CO₂ flow just below the critical point of the flowing mixture (106 bar at 100 °C if no 1-octene has been converted) was the best condition for the hydroformylation. It gave the highest acitivity (conversion to aldehyde up to 70 %), fastest reaction (TOF up to 575.3 h⁻¹) and best stable selectivity ( l:b ratio reaching 3.37 ). The utilization of scCO₂ as reaction media leads to remarkable stability of the catalyst. The supercritical or near critical (expanded liquid) system completely overcame the progressive decrease in activity of catalyst at 50, 75 bar with liquid phase transport and also showed much better results than when using other gas flows such as N₂ flow at 100 bar. In the high pressure scCO₂ phase, the concentration of 1-octene at the catalyst bed was reduced so that the conversion to aldehyde was reduced. The pore size and surface groups of the solid support should be suitable for the SILP catalyst consisting of metal complex, excess ligand and ionic liquid. Using microporous carbon aerogels as the supports, whether activated or not, gave disappointing results.

Thesis advisor: Kian L. Tan / Thesis advisor: James P. Morken / Described herein are four different research projects spanning over two different research groups. The first two projects describe the development and application of scaffolding catalysts for the (1) site-selective silylation of ribonucleosides and (2) the distal and diastereoselective hydroformylation of homoallylic alcohols. These projects emphasize the effectiveness of scaffolding catalysts to bind a hydroxyl-containing substrate and control the site- or regioselectivity of a reaction using said substrate. The third project describes a hydroxyl-directed diboration of homoallylic and bis-homoallylic alcohols. The hydroxyl-containing 1,2-bis(boronates) are valuable intermediates for further synthetic manipulations. One such manipulation, a hydroxyl-directed Suzuki cross-coupling reaction, is the focus of the final project. This directed cross-coupling reaction forges carbon-carbon bonds in a stereoselective manner, highlighted in the total synthesis of the naturally occurring compound, debromohamigeran E. / Thesis (PhD) — Boston College, 2015. / Submitted to: Boston College. Graduate School of Arts and Sciences. / Discipline: Chemistry.

Thesis advisor: James P. Morken / This dissertation describes the development of four metal-catalyzed carbon-carbon bond forming methods. The first project presented is a palladium-catalyzed proparyl-allyl cross-coupling which proceeds via a kinetic resolution to give enantioenriched 1,5-enynes. Next the asymmetric rhodium-catalyzed hydroformylation of 1-alkenes is described. This reaction delivers synthetically useful a-chiral aldehydes in up to 98:2 er and up to 15:1 branched to linear ratio. The development of a unique nickelcatalyzed asymmetric Kumada coupling of cyclic sulfates is presented. Mechanistic studies reveal the reaction proceeds via an SN2 oxidative addition of a chiral nickelcomplex. Finally, a-Substituted allyl bis(boronic) esters, which are derived from 1,2-diboration of 1,3-dienes are shown to undergo allylation and subsequent Suzuki coupling with aldehydes tethered to sp2 electrophiles. The carbocycle products obtained bear three contiguous stereocenters and were used as intermediates in the synthesis of complex molecules. / Thesis (PhD) — Boston College, 2017. / Submitted to: Boston College. Graduate School of Arts and Sciences. / Discipline: Chemistry.

Thesis advisor: Kian L. Tan / Chapter 1. We reported the first synthesis of all-carbon quaternary centers via hydroformylations using a catalytic directing group. With the ability of reversibly and covalently binding to a substrate, and coordinating to a metal center, scaffolding catalyst 1.1 is able to direct the branch-selective hydroformylation of 1,1-disubstituted olefins under mild temperature. Chapter 2. We have designed and synthesized a chiral organocatalyst 2.11. This catalyst is able to covalently bind to one hydroxyl, and utilize the induced intramolecularity to stereoselectively functionalize the other hydroxyl within a cis-1,2-diol via electrophile transfer. Catalyst 2.11 was used in the desymmetrization of meso-1,2-diols under mild conditions (4 C to room temperature), leading to high yields and selectivities for a broad substrate scope. Chapter 3. Catalyst 3.1 and 3.6 were demonstrated to selectively bind to primary hydroxyls over secondary hydroxyls. By combining the binding selectivity with asymmetric catalysis, these scaffolding catalysts were shown to promote the selective silylation of secondary hydroxyls within terminal (S)-1,2-diols. The reversal of substrate bias was further applied to a regiodivergent kinetic resolution of racemic terminal 1,2-diols, producing secondary protected products in synthetically practical levels of enantioselectivity (>95:5 er) and yields (≥40%). Time course studies of this reaction further revealed the optimal condition to form the primary silylated product in high s-factor. Chapter 4. Based on the previous understanding of catalyst 4.5 and 4.6, the exclusive catalyst recognition of cis-1,2-diols within polyhydroxylated molecules was further discovered. This unique functional group display recognition was further allied with the catalyst's ability to stereoselectively differentiate hydroxyls within cis-1,2-diols, enabling the site-selective protection, functionalization, and activation of the inherently less reactive axial hydroxyl groups within carbohydrates. This methodology also enables the selective functionalization of multiple complex molecules, including digoxin, mupirocin, and ribonucleosides, demonstrating the potential power of scaffolding catalysis in the rapid access to valuable synthetic derivatives of polyhydroxylated compounds. / Thesis (PhD) — Boston College, 2013. / Submitted to: Boston College. Graduate School of Arts and Sciences. / Discipline: Chemistry.

Both products, n-butyraldehyde and iso-butyraldehyde from propene hydroformylation are key building blocks for the synthesis of many chemical intermediates, and although high linear selectivity has been achieved, any form of branched selectivity remains very difficult to attain. This project aims to deliver a catalyst that can selectively produce branched iso-butyraldehyde as the major product from propene hydroformylation. One approach discussed is to study terphenyl phosphines as ligands. The synthesis of substituted terphenyls through Suzuki-Miyaura coupling reactions between aryl boronic acids and 2,6-dichloroanisole was studied. Novel phosphine-phosphanamine ligands with bulky terphenyl substituents were synthesised and tested in propene hydroformylation, and also asymmetric hydroformylation of other alkenes. The synthesis of several ferrocene-based phosphine-phosphoramidite ligands is also discussed. These ligands were then tested in rhodium-catalysed propene hydroformylation and their reactivities and selectivities are reported. These ligands/Rh catalysts showed a moderate reactivity for propene hydroformylation and up to 56% branched selectivity, which is close to the best selectivity known under industrially relevant conditions. The introduction of bulky substituents on the phosphoramidite part of the ligand did not deliver any huge increases in regioselectivity, but a large improvement in catalyst thermal stability was observed in experiments conducted using in situ high pressure infrared spectroscopy. The reaction conditions for rhodium-catalysed propene hydroformylation using the BOBPHOS ligand were investigated, with unprecedented branched selectivity of up to 82% achieved. A variety of aspects was examined, including the solvent, reaction temperature, reaction pressure with varying partial pressure of CO and H₂, and rhodium to ligand ratio. BOBPHOS derivatives which are more synthetically accessible and economically attractive were synthesised and tested in rhodium-catalysed propene hydroformylation. Comparable results with their parent ligand/Rh catalyst were obtained and improved thermal stabilities were observed in selected catalysts. Different directions for potential future works are suggested, which hopefully, along with the findings in this thesis, can be a major contribution to the development of an efficient, branched selective catalytic system for industrial propene hydroformylation.