Transfer hydrogenation has been recognized to be an important synthetic method in both academic and industrial research to obtain valuable products including alcohols. Transition metal catalysts based on precious metals, such as Ru, Rh and Ir, are typically employed for this process. In recent years, iron-based catalysts have attracted considerable attention as a greener and more sustainable alternative since iron is earth abundant, inexpensive and non-toxic. In this work, a combination of iron disulfide with chelating bipyridine ligand was found to be effective for the transfer hydrogenation of a variety of ketones to the corresponding alcohols in the presence of a simple base. It provided a convenient and economical way to conduct transfer hydrogenation. A plausible role of sulfide next to the metal center in facilitating the catalytic reaction is demonstrated.

京都大学 / 0048 / 新制・課程博士 / 博士(工学) / 甲第19181号 / 工博第4058号 / 新制||工||1626(附属図書館) / 32173 / 京都大学大学院工学研究科物質エネルギー化学専攻 / (主査)教授 中村 正治, 教授 辻 康之, 教授 小澤 文幸 / 学位規則第4条第1項該当 / Doctor of Philosophy (Engineering) / Kyoto University / DGAM

<p> The acetate-catalyzed bromination of acetone is shown to occur by an enolization mechanism, although the reactions involved in this process are more complex than has been supposed.</p> <p> A study of the activation parameters for the enolization of some bromoacetones, and an observed linear free energy relationship between enolization rate constants, and acid ionization constants, shows that the transition state for this process resembles enolate and not enol.</p> <p> Bromine substitution in ketones accelerates enolization rates on both sides of the carbonyl group.</p> <p> The acetate-catalyzed enolization of 2-butanone favours the methylene group by a factor of nearly two. This fact is interpreted in terms of methyl groups being inductively electron-withdrawing in their effect in forming an enolate transition state.</p> / Thesis / Doctor of Philosophy (PhD)

<p> The regioselectivities of bromination and deuterium exchange of 2-butanone are shown to be the same, under identical conditions. This work firmly establishes that enolization is the rate-determining step for the former reaction, contrary to some recent reports in the literature.</p> <p> The steric effects and activation parameters in the bimolecular nucleophilic displacement reactions of a series of α-haloketones and alkyl halides are shown to be inconsistent with either a bridging or conjugation mechanism for the observed rate enhancements of haloketone over alkyl halide.</p> <p> The stereoelectronic requirements of this mechanism are tested in a system where the stereochemistry is known (cis- and trans-chlorocyclohexanones). The activation parameters suggest that only in the case where the geometry is correct for maximum conjugation (trans-chlorocyclohexanone) is there an appreciable difference in mechanism (stereoelectronically) from displacement at ordinary saturated carbon.</p> / Thesis / Doctor of Philosophy (PhD)

Organoboron compounds are viewed as a crucial intermediate for a wide variety of reactions. The most notorious reaction that exemplifies the capability of organoboron reagents is the Suzuki-Miyaura cross-coupling reaction, which is used to generate carbon-carbon bonds under mild conditions. Because of the versatility of organoboron reagents, methods to selectively install boron remains crucial. Boron containing compounds have recently garnered significant interest in the medicinal chemistry field. Boron's unique properties allows the development of potential new boron-based drugs targeting novel signaling pathways with great efficacy. This dissertation describes the use of a diboron reagent to install boron on the electron withdrawing allenoate scaffold as well as on disubstituted 1,3-diynes. Lastly, this dissertation will cover the preliminary anti-fungal activity of a novel oxaborole scaffold. We investigated the borylation of the electron withdrawing allenoate scaffold. Reports in the literature were scarce and limited in the scope of the work or required the use of less available diboron reagents. We developed a method for the addition of the diboron reagent B2pin2 and a copper chloride catalyst at 60 °C to generate the (Z)-β-borylen-oate in an 18 – 81% yield. A diverse substrate scope was produced, with the reaction being very tolerable with both electron donating and electron withdrawing functional groups attached to the phenyl ring with yields ranging from 29 – 81%. To our delight as well, straight alkyl chains maintained the respective Z stereoselectivity while having yields range from 46 – 60%. During the reaction, activation of the diboron reagent using the copper catalyst in methanol then undergoes boryl-cupration that can subsequently be protonated to form the Z-product. The steric effect of the activated boron complex and the allenoate drives the stereoselectivity of the reaction. To continue the borylation of unique scaffolds, we developed a selective cis phosphinoboration of 1,3-diynes. In this reaction, a catalytic amount of tributyl phosphine and a diphenyl(4,4,5,5-tetramethyl-1-3-2-dioxaborolan-2-yl)phosphane is used to generate the corresponding cis 1,2-phosphinoboronate in yields ranging from 18 – 75%. The reaction is performed in dichloromethane at 40 °C. Substrates bearing an electron donating group on the phenyl ring resulted in the need for a longer reaction time and decreased yields (18 – 39%), while substrates bearing an electron withdrawing groups resulted in increased yields (55 – 72%). The phosphinoboration reaction was also tolerable towards heterocycles (64%) and alkyl groups (34 – 53%). This reaction is able to attach both boron and phosphorous simultaneously without the use of a transition metal. Mild oxidation using iodine resulted in oxidation of the phosphorous. The resulting product interestingly generated a B-O-P heterocycle. In medicinal chemistry, new boron containing scaffolds have shown promising preliminary anti-fungal activity. The oxaborole scaffold is widely seen as a privileged scaffold due to the unique ability of boron to behave as a pharmacophore. The five-membered ring in the oxaborole scaffold also enhances the Lewis acidity of the boron. Our group has previously identified a synthetic route in obtaining a novel 3-monosubstituted oxaborole scaffold. Herein, we have developed a small library of compounds that were tested against a variety of fungal strains. Assaying the library at 25 μg/mL identified multiple hits that allowed the development of a preliminary structure activity relationship profile. Compounds containing electron withdrawing groups on the phenyl ring demonstrated higher anti-fungal activity. This phenomenon is explained due to the change in Lewis acidity of the compound. Incorporating electron withdrawing groups increases the overall Lewis acidity of the oxaborole scaffold, and therefore allowing for stronger covalent interactions in the active site. Increasing the length of the scaffold resulted in a drastic loss in activity, suggesting a smaller scaffold is a necessity. Compounds containing a 4-fluoro, 4-chloro, 4-trifluoromethoxy, and 4-tetrafluoromethoxy were all compounds that consistently observed below 30% cell survival in the candida albicans, aspergillus niger, metarhizium anisopliiae, aspergillus flavus, penicillum chrysogenum, and saccharomyces cerevisiae fungal assays. To further explore the promising potential of the new scaffold, minimum inhibitory concentrations for our lead compounds will be conducted in the future. / Doctor of Philosophy / Boron-containing compounds are prevalent in a multitude of chemical reactions. Due to the versatility of organoborons in chemical transformations, the development for new chemical reactions that install boron is vital. Of great importance in the installation is the ability to perform the reactions under mild conditions and low cost under environmentally friendly fashion. Boron-containing drugs are also a unique scaffold due to the ability boron has in its ability to act as a drug. Boron is able to covalently bind to molecules in the active site, creating an "anchor" that can then therefore deliver the respective therapeutic effect. This dissertation discusses two reactions that install boron in a selective fashion on challenging substrates. The first chapter discusses the installation of boron on a challenging allene scaffold. The focus of the installation is to maintain selectivity of where the boron ends up on the resulting product which we were successful in. The following chapter discusses the installation of both boron and phosphorous in a one-step fashion. Previous methods would require more steps, harsher conditions, and lower overall yields while we can now circumnavigate these challenges in our new method. The third part of my dissertation will discuss the discovery of a novel boron-containing drug scaffold that has promising anti-fungal activity. Anti-fungal drugs are usually difficult to come by, allowing for our scaffold to shine in a challenging field. We have identified multiple hits in our preliminary assays and we can show that manipulating the potential reactivity of the boron can result in greater or lesser anti-fungal activity.

This thesis is the use of commercially available methyl 2-iodobenzoate as the starting material and was prepared into iodine - oxazoline compound 118. Then, we undergo copper-catalyzed cross-coupling reactions of compound 118with thiols, and were readily facilitated to afford the corresponding desired products 127¡B136 in good to excellent yields. This method not only modified short- comings of that adding strong base to synthesis of sulfur-oxazoline ligands in past years but also has a good yield performances, the yield is 70 -87%. And we will use this strategy to undergo one pot reaction of carbon-sulfur coupling in future. In the end, we used new sulfur-oxazoline ligands127¡B128 in the Pd-catalyzed asymmetric alkylation of 1,3-diphenyl-2-propenyl acetate with dimethyl malonate. and reaction ee% were high, with the best result of 99% and 93% conversion.

Developing asymmetric C-H bond activation methods in order to achieve enantiopure products is crucial for the advancement of the field and for the production of novel chiral compounds. Therefore, we tried to develop this area of organic chemistry by presenting metal catalyzed stereoselective C-H bond activation utilizing chelation-assisted tools. The first section of this study involves Rh(I) catalyzed asymmetric C-H bond activation of a series of ketones via an intermolecular procedure. By this method, we examine ortho-alkylation of aromatic ketones and β-functionalization of α-β unsaturated ketones with a series of prochiral olefins. In the second section, we present an efficient three steps method for stereoselective intramolecular C-H bond activation of indol-3-carboxaldehyde with tethered prochiral olefins. The catalytic system in both methods involves a joint chiral primary amine and Rh(I) catalyst. Chiral primary amines can serve to induce enantioselectivity as well as acting as a useful directing group which has shown appropriate coordination to the transition metal catalyst, providing high regioselectivity. / February 2017

<p>The wide presence of C-N bonds in biologically and pharmaceutically important compounds continues to drive the development of new C-N bond-forming transformations. Among the different strategies, electrophilic amination is an important synthetic approach for the direct formation of C-N bonds. Compared to electrophilic amination of organometallic reagents, direct amination of C-H bonds will provide a potentially more effective route towards C-N bond formation. Towards this, we proposed an electrophilic amination of C-H bonds via their reactive organometallic surrogate intermediates. Specifically, we are interested in organozinc intermediates and their in situ formation from C-H bonds. </p><p>This dissertation reports our development of direct amination of various C-H bonds using a H-Zn exchange/electrophilic amination strategy as a rapid and powerful way to access a variety of functionalized amines. We were able to achieve C-H zincation using strong and non-nucleophilic bases Zn(tmp)2 or tmpZnCl*LiCl and subsequent electrophilic amination of the corresponding zinc carbanions with copper as a catalyst and O-benzoylhydroxylamines as the electrophilic nitrogen source. With such a one-pot procedure, the synthesis of various amines from C-H bonds has been achieved, including alpha-amination of esters, amides, and phosphonates. Direct amination of heteroaromatic and aromatic C-H bonds has also been developed in good to high yields. It is important to note that mild reactivity of organozinc reagents offers a good compatibility with different functional groups, such as esters, amides, and halides. </p><p>Success in developing direct and efficient syntheses of these various amines is highly valuable. These new amination methods will greatly expand the chemical diversity and space of available amine skeletons, and will contribute to future advances in material science, medicinal chemistry and drug discovery.</p> / Dissertation

Biomass burning aerosols play an important role in the chemistry and physics of the atmosphere and therefore, affect global climate. Biomass burning aerosols are generally aqueous and have a strong saccharidic component due to the combustion and pyrolysis of cellulose, a major component of foliar fuel. This class of aerosol is known to affect both the absorption and scatter of solar radiation. Also, biomass burning aerosols contribute to cloud formation through their action as cloud-condensation nuclei. Many questions exist about the chemical speciation and chemical aging of biomass burning aerosols and how this affects their atmospheric properties and ultimately, global climate. Also, knowledge of the chemical components of these aerosols is important in the search for chemical tracers that can give information about the point or regional source, fuel type, and age of a biomass burning aerosol parcel. Levoglucosan was chosen for these studies as a model compound for biomass burning aerosols because of its high measured concentrations in aerosol samples. Levoglucosan often dominates the aerosol composition by mass. In this dissertation, laboratory proxy systems were developed to study the solution-phase chemistry of levoglucosan with common atmospheric reactants found in biomass burning aerosols (i.e. H+, •OH). To mimic these natural conditions, acid chemistry was studied using sulfuric acid in water (pH=4.5). The hydroxyl radical (•OH) was produced by the Fenton reaction which consists of iron, hydrogen peroxide and acid (H2SO4) in aqueous solvent. For studies in aqueous sulfuric acid, oligomers of levoglucosan were measured by matrix-assisted laser desorption and ionization time-of-flight mass spectrometry (MALDI-TOF-MS). A rational mechanism is proposed based on both the acid-catalyzed cationic ring-opening of levoglucosan and nucleophilic attack of ROH from levoglucosan on the hemi-acetal carbon to produce pyranose oligomers through the formation of glycosidic bonds. Oligomer formation is further supported by attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR). Reactions of levoglucosan with •OH produced from Fenton chemistry were studied in solution. Two modes of oligomerization (2000 u) were observed for reaction times between 1 and 7 days using MALDI-TOF-MS and laser desorption ionization (LDI) TOF-MS. Single-mass unit continuum mass distributions with dominant -2 u patterns were measured and superimposed by a +176/+162 u oligomer series. This latter oligomer pattern was attributed to a Criegee rearrangement (+14 u) of levoglucosan, initiated by •OH, forming a lactone (176 u). The acid-catalyzed reaction of any ROH from levoglucosan (+162 u) forms an ester through transesterification of the lactone functionality, whereupon propagation forms polyesters. Proposed products and chemical mechanisms are suggested as sources and precursors of humic-like substances (HULIS), which are known to possess a large saccharic component and are possibly formed from biomass burning aerosols. These products could also serve as secondary tracers, giving further information on the source and age of the aerosol.

The second order rate constants for nucleophilic substitution by methoxide of (Z)- and (E)-O-methylbenzohydroximoyl fluorides [C6H4C(F)=NOCH3] with various substituents on the phenyl ring [p-OCH3 (1h, 2h), p-CH3 (1g, 2g), p-Cl (1f, 2f), p-H (1e, 2e), (3,5)-bis-CF3 (1i, 2i)] in 90:10 DMSO:MeOH have been measured. A Hammett plot of these rate constants vs σ values gave positive ρ values of 2.95 (Z isomer) and 3.29 (E isomer). Comparison of these rates with methoxide substitution rates for Omethylbenzohydroximoyl bromide [C6H4C(Br)=NOCH3] and Omethylbenzohydroximoyl chloride [C6H4C(Cl)=NOCH3] reveal an element effect for the Z isomers of Br:Cl:F(1e) = 2.21:1.00:79.7 and for the E isomers of Cl:F(2e) = 1.00:18.3. With the p-OCH3-imidoyl halides the following element effects are found: Br:Cl:F(1h) = 2.78:1.00:73.1 for the Z isomer and Br:Cl:F(2h) = 1.97:1.00:12.1 for the E isomer. Measurement of activation parameters revealed ∆S≠ = -17 eu for 1e and ∆S≠ = -9.9 eu for 2e. Ab initio calculations (HF/6-31+G*, MP2/6-31+G*//HF/6-31+G*, B3LYP/6- 31+G*//HF/6-31+G*, HF-SCIPCM/6-31+G*//HF/6-31+G*) were performed to define the reaction surface. These calculations demonstrate a relatively large barrier for nucleophilic attack in relation to halogen loss and support the experimental findings that this reaction proceeds by an addition-elimination mechanism (AN# + DN). The imidoyl fluorides have been used to synthesize highly functionalized O-methyloximes by reaction with enolate anions derived from malononitrile, ethyl cyanoacetate, and diethyl malonate. Acid-catalyzed isomerization of compounds containing the O-methyloxime moiety have been investigated with ab initio calculations (HF/6-31+G*, MP2/6- 31+G*//HF/6-31+G*, B3LYP/6-31+G*//HF/6-31+G*). Barriers for rotation around the C-N bond following protonation have been calculated. The calculated barriers are discussed in relation to an isomerization mechanism of protonation-rotation versus a nucleophilic catalysis.