M.Sc. (Chemistry) / Loading gold nanoparticles (Au NPs) on mesoporous materials via different methods has been reported in the literature. However, the immobilisation of the dendrimer-encapsulated Au NPs on materials is still considered amongst the hot topics in chemistry. This study describes the synthesis, characterisation as well as catalytic evaluation of unsupported and supported Au NPs....

M.Sc. / There were two main objectives of the research presented m this dissertation. Firstly, the synthesis of bulky electron withdrawing phosphine-alkene ligands for classic ligand testing in the Suzuki cross-coupling reaction was performed. Previously, a range of electron deficient phosphine-alkenes was prepared from 2- ( diphenylphosphino )benzaldehyde, using both Wittig and Knoevenagel chemistry. These were tested for catalysis and gave high yields for the Suzuki reaction. In the present instance, 2-( di-otolylphosphino) benzaldehyde was synthesised making use of Grignard technology from acetyl protected 2-bromobenzaldehyde and chloro(di-o-tolyl)phosphine (itself prepared from PCh. And the appropriate o-tolyl Grignard reagent. This material served as a building block for the generation of P-alkene ligands which were synthesised making use of Wittig, Knoevenagel and transesterification chemistry. These o-tolyl analogues of the P-alkene ligands prepared in the previous study were used in ligand testing experiments in the Pd-catalysed Suzuki cross-coupling reaction. The results of the catalysis showed an enhanced activity with these ligands over the previous cases The second part of this dissertation involved determining the role (influence on activity) of the non coordinating counterion in the catalyst system in the methoxycarbonylation reaction. To this end discrete Pd complexes were synthesised and used directly in the methoxycarbonylation reaction. There have been a few reports on the role of the non-coordinating counterions of the catalyst systems in the methoxycarbonylation reaction. The catalyst is typically a palladium compound in the presence of a Bmnsted acid co-catalyst. Changes to the Bmnsted co-catalyst cause two variables to change, namely the acidity of the acid and the nature of the counterion that the acid provides. The work presented in this dissertation shows the results of only one variable being changed (that of the counterion) and as such allowed the specific role of the counterion in the outcome of the reaction to be determined. Previous work done in our laboratories made use of the Lewis acid Al(OTf)3 to co-catalyse the methoxycarbonylation reaction with rates and high yields being observed. In the present instance discrete Pd complexes were synthesised from Pd(OAc)2 using p-TsOH, MsOH and TfOH as the acids containing the weakly coordinating counterions. These Bnmsted acids have the ability to displace the OAc- anion from the Pd and as such formed the discrete L2PdX2complexes (L = PPh3; X = Mso-, p-Tso-, TfO} Synthesis of these discrete complexes was impeded by a lack of knowledge of the specific conditions under which to prepare the complexes and many avenues were pursued before successful isolation of these complexes was achieved. These discrete catalysts were used in the methoxycarbonylation reaction co-catalysed by Al(OT£)3. Here, the Al(OTt)3 forms the basis of a constant acid cocatalyst allowing only the counterion to be changed with the view to determining its role in these reactions. It was found that the counterion appears to play no role at all (Aco-, p-Tso-, Mso-, TfO-) in the outcomes of these reactions under the conditions employed. A comparative study is also detailed herewithin of the effects of both ex situ and in situ catalyst generation on the activity in the methoxycarbonylation reaction, which provides some insightful results.

(+)-(2R,3R)-1,1,4,4-Tetraphenylbutane-1,2,3,4-tetraol (TETROL) and its derivatives were reacted with varying molar ratios of titanium isopropoxide (2:1, 1:1 and 1:2 tetraol:titanium isopropoxide) in an attempt to prepare potential titanium-based tetraol catalysts for enantioselective transformations. In each case, infrared and HNMR spectra suggested that the product was formed. We tentatively proposed that the structure of the catalyst was a spiro-type, but we could not determine conclusively what its exact structure was, despite using numerous techniques at our disposal (molecular modelling calculations, H NMR and IR spectroscopy, thermal analyses, powder diffraction, and single crystal X-ray diffraction). The catalyst and derivatives thereof were able to act catalytically for the enantioselective additions of diethylzinc compounds to aldehydes. The effects of temperature and solvent were investigated, and toluene and -78 °C were selected as optimal from the results obtained. (The reaction could, however, not be maintained at this low temperature for extended periods due to the fact that we did not have, at our disposal, the correct equipment. Each 16 h reaction was thus allowed to reach room temperature in each case.) The selectivity for the product 1-phenylpropan-1-ol (when benzaldehyde was the starting aldehyde) varied depending on the nature of the aryl substituents of the titanium-based catalyst. Using 0.2 molar equivalents of the chiral titanates, the highest selectivity was 42 percent (e.e.), but only when excess Ti(O-i-Pr)4 had been added to the reaction mixture. This was achieved with the tetra(ortho-methoxyphenyl)-TETROLate derivative. TETROL and its derivatives were also successful in metal-free catalysis where higher conversions and selectivities were observed, compared to when these were complexed to titanium. The highest selectivity was 70 percent (e.e.), achieved with the tetra(ortho-methylphenyl)TETROL derivative.

Nanomaterials have become a popular topic of research over the years because of their many important applications. It can be a challenge to stabilize the particles at a nanometer size, while having control over their surface features. Copper nanoparticles were synthesized photochemically using a photogenerated radical allowing spatial and temporal control over their formation. The synthesis was affected by the stabilizers used, which changed the size, dispersity, rate of formation, and oxidation rate. Copper nanoparticles suffer from their fast oxidation in air, so copper-silver bimetallic nanoparticles were synthesized in attempts to overcome the oxidation of copper nanoparticles. Bimetallic nanoparticles were synthesized, but preventing the oxidation of the copper nanoparticles proved difficult. One important application of nanoparticles that was explored here is in catalyzing organic reactions. Because of the fast oxidation of copper nanoparticles, silver nanoparticles were synthesized photochemically on different supports including TiO2 and hydrotalcite (HTC). Their catalytic efficiency was tested using alcohol oxidations. Different silver nanoparticle shapes (decahedra and plates) were compared with the spheres to see the different catalytic efficiencies.

This thesis examines the catalytic characteristics of two materials with respect to the decomposition of Formic Acid. The decomposition of formic acid proceeds via two principal reaction pathways: dehydration and dehydrogenation. Dehydrogenation is a valuable reaction producing Hydrogen suitable for use in fuel cells whereas the dehydration pathway produces carbon monoxide, a poison for many fuel cell materials. One of the surface species, the formate ion, is also implicated in other important chemical reactions, most notably the water gas shift and the decomposition of methanol. The author seeks to document various intermediate surface species associated with the two reaction pathways with hope to use this information to future tailoring of catalysts for greater selectivity.

As the world moves forward to the development of biorefineries, the interest to replace chemicals and materials derived from petroleum is increasing exponentially. Lignin is a macromolecular by-product derived from the wood pulping industry, mainly used for heating purposes. The development of new processes to produce high value-added lignin products such as multifunctional aromatic chemicals and high-tech carbon materials are required to fulfill the needs for biorenewable feedstocks. Such processes are likely to include selective oxidation catalysis. The aim of this Thesis is to advance the state-of-the-art for the oxidation of lignin models and lignin extracts using homogeneous catalysts based on vanadium, an inexpensive and abundant transition metal, using air as the only oxidant. Lignin models containing the most important features of lignin (e.g., β-O-4 and β-1 linkages) were initially used to assess the catalytic potential. Previously reported (HQ)2V(O)(OiPr) and (dipic)V(O)(OiPr) catalysts (dipic = dipicolinate and HQ = 8-oxyquinoline) displayed different selectivity for C-H, C-O and C-C bond cleavage upon varying of the solvent, the lignin model or the catalyst. Moreover, these catalysts cleave the C-H bond of secondary alcohols through a two-electron oxidation process and the C-C bond cleavage of the oxidation product ketone in the presence of exogenous base. Several amine bis(phenolate) oxovanadium(V) catalysts were synthesized and fully characterized, and demonstrated very good activity for the oxidation of lignin models and the depolymerization of organosolv lignin. These new catalysts overcome the need for added base, display higher reaction rates of oxidation, and improve the selectivity for the disassembly of lignin models. The different selectivities involving C-H vs. C-O vs. C-C bond cleavage are discussed together with a novel redox-neutral C-C bond cleavage of lignin model 1,2-diphenyl-2-methoxyethanol. The oxovanadium(V) catalysts, along with a metal-free variant and other transition metal catalysts, were employed to assess their performance for the oxidation and depolymerization of organosolv lignin. Although most catalysts oxidized the lignin extracts, the oxovanadium(V) complexes demonstrated the highest degree of lignin depolymerization as shown by Gel Permeation Chromatography (GPC), quantitative-Heteronuclear Single Quantum Correlation (q-HSQC) and quantitative 31P NMR spectroscopy of derived phosphite esters. In a complementary study, oxovanadium(V) catalysts also established their utility for the valorization of cellulose-derived substrates (e.g., diols). Two trialkoxyamine oxovanadium(V) complexes bearing a triethoxyamine and tris[2-(3,5-di-tert-butyl-phenoxy)methyl]amine ligand respectively, selectively cleaved the C-C bond in 1,2-diols with excellent rates and using air as the only oxidant. In a stoichiometric investigation of this reaction, it was determined that the transformation proceeds through an unusual direct oxidative two-electron cleavage of diols, affording a non-oxo monometallic V(III) intermediate. DFT calculations support a single-site proton-coupled electron-transfer of the hydroxyl hydrogen to the V oxo orbital. In summary, this Thesis describes new developments in vanadium catalysis such as mechanistic implications and catalyst optimization for the valorization of lignocellulosic biomass utilizing air as an oxidant.

>Magister Scientiae - MSc / This thesis reports on the syntheses of new bimetallic iminopyridyl nickel(II) and palladium(II) complexes as catalyst precursors for ethylene ligomerization/polymerization. Tetrahydrophenyl-linked iminopyridyl ligands, pyridin-2-ylmethyl-{4-[(pyridin-2-ylmethylimino)-methyl]-benzylidene}-amine (L1) and (2-pyridin-2-yl-ethyl)-{4-[(2-pyridin-2-yl-ethylimino)-methyl]-benzylidene}-amine (L2) were prepared via condensation from terephthaldehyde and 2 molar equivalents of a primary pyridylamine. Alkyl-linked iminopyridyl ligands N,N'-bis-pyridin-2-ylmethylene-propane-1,3-diamine (L3), N,N'-bispyridin- 2-ylmethylene-butane-1,4-diamine (L4) and N,N'-bis-pyridin-2-ylmethylenepentane- 1,5-diamine (L5) were prepared by condensation of 2 equivalents of 2- pyridinecarboxaldehyde and a primary diamine. The ligands were obtained as either red oils or orange solids. These ligands were characterized using Fourier-transform infrared spectroscopy (FTIR), nuclear magnetic resonance spectroscopy (NMR), mass spectrometry (MS), elemental analysis (EA), ultraviolet-visible spectrophotometry (UV-Vis) and thermal gravimetric analysis (TGA) where applicable. The tetrahydrophenyl-linked iminopyridyl ligands were subsequently used to prepare their corresponding homobimetallic palladium(II) and nickel(II) complexes. A 1:2 reaction of the ligands with PdCl2(COD), NiCl2(DME) and NiBr2(DME) gave palladium(II) and nickel(II) complexes C1-C6 in moderate to very good yields (58-94%). The palladium(II) complexes were found to be stable, but light-sensitive solids while the nickel(II) complexes were found to be stable, but light and air sensitive solids. These complexes were characterized using FTIR, NMR, EA, MS, UV-Vis and TGA. These complexes were then tested for catalytic activity of ethylene oligomerization. It was found that complexes C1 and C5 were highly active when activated by the cocatalysts methylaluminoxane (MAO) as well as ethyl aluminium dichloride (EADC). It was found that EADC gave the highest activity so the remaining catalysts (C3 and C6) were tested exclusively with EADC. All four complexes were active for ethylene oligomerization with yields of between 2.7-6.5 g, with C5 providing the highest activity and C1 the lowest. These catalysts were highly selective towards C4 oligomers with percentages ranging from 71-81%. Optimization studies were then carried out with C3 by varying the pressure and Al:Ni ratio.

京都大学 / 0048 / 新制・課程博士 / 博士(工学) / 甲第22453号 / 工博第4714号 / 新制||工||1736(附属図書館) / 京都大学大学院工学研究科材料化学専攻 / (主査)教授 松原 誠二郎, 教授 杉野目 道紀, 教授 中尾 佳亮 / 学位規則第4条第1項該当 / Doctor of Philosophy (Engineering) / Kyoto University / DGAM

CO2 is generally regarded as a waste product. However, the efficient catalytic reduction of CO2 means that this concept can change to viewing this molecule as a feedstock to produce chemically valuable products. The catalytic reduction of CO2 is a challenge because of its stability, and its reduction into chemically valuable products requires an appropriate catalyst and accessible energy source. While second and third row transition metals have shown considerable promise as photocatalysts for the reduction of CO2 to CO, one of our goals is to elaborate on the metal centers and the ligand environments in order to discover new catalysts and processes. These efforts have revealed new photocatalysts based on manganese and rhenium supported by κ2-PN phosphinoaminopyridine ligands. This thesis will describe the synthesis and characterization of these catalysts and their CO2 reduction parameters. The selectivity of these catalysts for either CO or HCOOH will be explored. Furthermore, ligand modifications and their effects on the catalyst behaviour will also be presented.

Thesis advisor: Amir H. Hoveyda / Homoallylic amines and alcohols, particularly those amenable to further functionalization, are among the most widely used building blocks in chemical synthesis and are typically accessed by addition of an allyl-metal compound to an electrophile. Studies discussed herein have focused on advancing stereoselective synthesis of versatile allylboron compounds and their utilization in catalytic regio-, diastereo-, and enantioselective addition to various electrophiles. Mechanistic principles have been central to the investigations described in this thesis, and it has been on this basis that catalytic strategies for practical synthesis of bioactive molecules were developed. Chapter One. Vicinal amino alcohols are ubiquitous in natural products and serve as versatile synthetic intermediates and we envisaged that diastereo- and enantioselective additions of O-substituted allyl boronates offers an attractive option to access these motifs. In the presence of zinc (II) methoxide as co-catalyst, it will be demonstrated that sequence of events may occur, wherein isomerization of an initially formed allyl complex occurs prior to addition of an aldimine with kinetic selectivity. As will be described, through the use of an optimal catalyst, N-protecting/activating group and appropriate reaction conditions, differentially protected vicinal amino alcohol derivatives may be synthesized in high enantiopurity. The utility of the approach is highlighted through synthesis of an NK1 agonist. Chapter Two. It will be demonstrated that additions of various organoboron compounds converts readily accessible and easy-to-handle silyl-substituted -tertiary amines. Contrary to additions to aldimines, isomerization of the initially generated aminophenol-allyl complex is preempted, suchthat linear products are favored. DFT analysis suggests that high enantioselectivity likely originates from attractive electrostatic interaction between a trifluoromethyl group and the catalyst’s ammonium moiety. The synthetic utility was highlighted through concise, enantioselective synthesis of a key intermediate of a recently reported BACE-1 inhibitor on gram scale. Chapter Three. This section details the development of a method for direct synthesis of homoallylic alcohols bearing a Z-alkenyl chloride, which may be directly subjected to stereo-retentive cross coupling without wasteful protection/deprotection or redox operations. Products were obtained in high regio- and enantioselectivity for aliphatic, alkenyl- and heteroaryl-substituted aldehydes. The approach was utilized in a concise, protecting group-free synthesis of anti-tumor agent mycothiazole. Chapter Four. A method for stereoselective synthesis of fluorine-containing trisubstituted allyl boronates will be presented. It will then be illustrated that in the presence of an appropriate aminophenol catalyst, a large assortment of homoallylic alcohols containing a quaternary fluoro- and trifluoromethyl-substituted stereogenic center may be obtained with efficiency and high diastereo- and enantioselectivity. The obtained products were then elaborated to the furanose core of Sofosbuvir, a recently approved treatment for hepatitis C. / Thesis (PhD) — Boston College, 2020. / Submitted to: Boston College. Graduate School of Arts and Sciences. / Discipline: Chemistry.