Bimetallic Catalysis is an emerging field of study that uses two metals to cooperatively perform organic transformations. These metals can serve to activate or bind substrates in order to increase the rate and selectivity of reactions. This work first describes the synthesis and utilization of six new chiral, titanium-containing phosphinoamide ligands. These Lewis acidic ligands withdraw electron density from an active palladium center to induce chirality and increase the rate of allylic amination of hindered, secondary N-alkyl amines. X-ray quality crystals were grown for each ligand and completed the allylic amination of hindered secondary amines in minutes whereas other non-titanium-containing ligands produced trace product. Although enantioselectivity was low initially, through a dynamic kinetic resolution enantioselectivity was increased over time, reaching 53% enantioselectivity. The second type of bimetallic catalysis discussed is dinuclear Pd(II) and Pd(I) catalysis. These dimers were built on a 2-phosphinoamide ligand scaffold and present interesting molecular structure and unique reactivity. These dimers were found to perform tandem arylketone coupling to produce disubstituted naphthalene products under oxidative conditions. It is proposed that the Pd(II) dimer undergoes oxidative addition to produce a Pd(III) dimer which subsequently produces an aryl-ketone intermediate. This process is made possible by the cooperativity of the two palladium centers which enable the formation of a Pd(III) dimer, circumventing the need for the high energy Pd(IV) oxidation state. Oxidative conditions then allows coupling and cyclization of a second ketone to form the naphthalene product.

京都大学 / 0048 / 新制・課程博士 / 博士(工学) / 甲第20584号 / 工博第4364号 / 新制||工||1678(附属図書館) / 京都大学大学院工学研究科合成・生物化学専攻 / (主査)教授 杉野目 道紀, 教授 吉田 潤一, 教授 大江 浩一 / 学位規則第4条第1項該当 / Doctor of Philosophy (Engineering) / Kyoto University / DGAM

A new approach was taken in the elucidation of the stereochemistry of the symmetrically 1,4-disubstituted 1,4-dihydronaphthalene systems which show deceptively simple NMR spectra. Thus, the stereochemistry of 1,4-di-tert-butyl-1,4-dihydronaphthalene was established unequivocally. The epoxide derivative, the subject compound, 1,4-di-tertbutyl-2, 3-epoxy-1, 4-dihydronaphthalene, was formed and its trans stereochemistry was established by ¹H NMR and ¹³C NMR. A lanthanide shift study was also conducted on the epoxide derivative, further proving the trans stereochemistry. One of the lanthanide shifted spectra was analyzed using the LAACOON III computer program and the true coupling constants obtained this way were in excellent agreement with the experimental spectrum. Establishing the trans stereochemistry of the epoxide derivative proved the trans stereochemistry of 1,4-di-tert-butyl-1,4-dihydronaphthalene.

Transition metal catalysis is a necessary branch of organic synthesis. Both monometallic and bimetallic catalysts can reduce reaction times, improve regio- and enantioselectivity, and minimize byproducts. Additionally, bimetallic catalysts can cooperatively activate substrates, which can enable new reactions and mechanistic pathways. The first half of this work will describe the synthesis and catalytic ability of our novel Pd(I) and Pd(II) dimers. Both dimers use a 2-phosphinoimidazole ligand scaffold to bring the metal centers in close proximity. The Pd(II) dimer can catalyze the synthesis of 1,3-disubstituted naphthalene rings from commercially available aryl iodides and methyl ketones with high regioselectivity and yields. Mechanistic and theoretical studies suggest the mechanism undergoes a Pd(III)–Pd(III) like intermediate. Additionally, we studied the impact of precatalyst oxidation state on C–N bonding reactions. We found that our Pd(I) dimer performed better in Buchwald-Hartwig aminations, while our Pd(II) dimer was shown to be extremely active in aminocarbonylation reactions. Both reactions gave C–N bonding products in good to excellent yield. The second portion of this work describes our novel Pd N–H NHC complex and its application in Suzuki-Miyaura cross couplings. In the presence of methanol, a Pd(II) salt will insert into the C–P bond of a 2-phosphinoimidazole ligand to give a protic NHC complex. The acidic hydrogen can be deprotonated under reaction conditions to give an anionic complex, which further increases the electron density on palladium as shown in Tolman Electronic Parameter studies. Application of the catalyst in Suzuki-Miyaura and Sonogashira coupling reactions gave product in high yield. Since our Pd N–H NHC complex with a diphenylphosphine ligand could not activate aryl chlorides, we then applied 2-dialkylphopshinoimidazole ligands. When the dialkyl ligands were stirred with Pd(II) salts in methanol, an equilibrium was observed between N–H NHC and P–N coordination complexes. When the catalytic mixture was applied to Suzuki-Miyaura cross-couplings, (hetero)aryl chlorides gave high yields with low catalyst loadings.

This work was concerned with the determination of mass transfer and kinetic parameters of ozone reactions with four organic compounds from different families, namely reactive dye RO16, triclocarban, naphthalene and methanol. In order to understand the mechanisms of ozone reactions with the organic pollutants, a radical scavenger (t-butanol) was used and the pH was varied from 2 to 9. Ozone solubility (CAL*) is an important parameter that affects both mass transfer rates and chemical reaction kinetics. In order to determine accurate values of the CAL* in the current work, a set of experiments were devised and a correlation between CAL* and the gas phase ozone concentration of the form CAL*(mol/L) = 0.0456 CO3 (g/m3 NTP) was obtained at 20°C. This work has also revealed that t-butanol did not only inhibit hydroxyl radical reactions but also increased mass transfer due to it increasing the specific surface area (aL). Values of the aL were determined to be 2.7 and 3.5 m2/m3 in the absence and presence of t-butanol respectively. It was noticed that the volumetric mass transfer coefficient (kLa) has increased following the addition of t-butanol. Ozone decomposition was studied at pH values of 2 to 9 in a 500 mL reactor initially saturated with ozone. Ozone decomposition was found to follow a second order reaction at pH values less than 7 whilst it was first order at pH 9. When the t-butanol was added, the decomposition of ozone progressed at a lower reaction order of 1.5 for pH values less than 7 and at the same order without t-butanol at pH 9. Ozone decomposition was found significant at high pHs due to high hydroxide ion concentration, which promotes ozone decomposition at high pHs. The reaction rate constant (k) of RO16 ozonation in the absence of t-butanol was determined. The result suggests that RO16 degradation occurs solely by molecular ozone and indirect reactions by radicals are insignificant. The chemical reaction of triclocarban with ozone was found to follow second order reaction kinetics. The degradation of naphthalene using the liquid/gas-ozone (LGO) system was studied. This result showed that hydroxyl radicals seemed to have limited effect on naphthalene degradation which was also observed when a radical scavenger (t-butanol) was used. Reaction rate constants were calculated and were found around 100 times higher than values reported in the literature due to differences in experimental conditions. From the results of the experimental investigation on the degradation of methanol by ozone it was found that the rate constant (k) of the degradation reaction increased at pH 9. The reaction stoichiometry was found to have a value of 1 mol/mol. The two steps of the liquid/solid-ozone (LSO) system were studied on beds of silica gel and a zeolitic material (D915) and the ozone adsorption process was modeled and found that particle rate controls ozone adsorption step but liquid rate controls the water treatment step. Ozone desorption with pure deionised water was studied. The water flow rate was found to accelerate the desorption rates but pH was found to decrease the desorption rates. In contrast, the effect of pH was insignificant in the presence of t-butanol. Determination of the adsorption isotherms for RO16, naphthalene and methanol revealed that RO16 did not exhibit adsorption on silica gel, but both naphthalene and methanol showed adsorption on D915 described by Langmuir model. / Education Service Department of the Libyan Government

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