The work in this thesis describes the development of new heteroarylation methodology based on transition metal-catalysed C-H functionalisation and the properties of organomain group compounds. The underlying reaction mechanisms and reactivity patterns of the (hetero)arene substrates are also investigated. The selective C2-H arylation indoles, which are key pharmaceutically-relevant units, was achieved using N-pyrimidyl directing groups, RuII catalysis and arylboronic acids as the coupling reagents (paper I). The use of this set of conditions enabled a remarkable functional group tolerance, highlighted by the preservation of halide substituents on both coupling partners. Mechanistic experiments suggest that cleavage of the C2-H bond occurs through an electrophilic aromatic substitution type pathway. The dehydrogenative C2-H silylation of unprotected gramine and tryptamine alkaloids and other related heteroarenes using hydrosilanes under Ru0 catalysis is described in paper II. The protocol does not require protecting groups and undirected C2-H silylation of heteroarenes is possible at higher temperatures. Significantly, H/D-exchange studies revealed deuterium incorporation at the C4 and C7 positions of the indole unit, apart from C2-H silylation. This study represents the first account of C4-H activation using an electron-rich metal catalyst. Paper III describes an unexpected and profound influence of boronate substituents on the regioselectivity of aryne trapping reactions. The boronates may be introduced easily to the backbone of established fluoride-activated precursors via Ir-catalysed C-H functionalisation. Optimisation and mechanistic studies on the unprecedented level of regioselectivity control these substituents permit using external additives is presented.

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The antiviral or anticancer activities of C-5 modified pyrimidine nucleoside analogues validate the need for the development of their syntheses. In the first half of this dissertation, I explore the Pd-catalyzed cross-coupling reaction of allylphenylgermanes with aryl halides in the presence of SbF5/TBAF to give various biaryls by transferring multiple phenyl groups, which has also been applied to the 5-halo pyrimidine nucleosides for the synthesis of 5-aryl derivatives. To avoid the use of organometallic reagents, I developed Pd-catalyzed direct arylation of 5-halo pyrimidine nucleosides. It was discovered that 5-aryl pyrimidine nucleosides could be synthesized by Pd-catalyzed direct arylation of N3-free 5-halo uracil and uracil nucleosides with simple arenes or heteroaromatics in the presence of TBAF within 1 h. Both N3-protected and N3-free uracil and uracil nucleosides could undergo base-promoted Pd-catalyzed direct arylation, but only with electron rich heteroaromatics. In the second half of this dissertation, 5-acetylenic uracil and uracil nucleosides have been employed to investigate the hydrogermylation, hydrosulfonylation as well as hydroazidation for the synthesis of various functionalized 5-vinyl pyrimidine nucleosides. Hydrogermylation of 5-alkynyl uracil analogues with trialkylgermane or tris(trimethylsilyl)germane hydride gave the corresponding vinyl trialkylgermane, or tris(trimethylsilyl)germane uracil derivatives. During the hydrogermylation with triphenylgermane, besides the vinyl triphenylgermane uracil derivatives, 5-[2-(triphenylgermyl)acetyl]uracil was also isolated and characterized and the origin of the acetyl oxygen was clarified. Tris(trimethylsilyl)germane uracil derivatives were coupled to aryl halides but with decent yield. Iron-mediated regio- and stereoselective hydrosulfonylation of the 5-ethynyl pyrimidine analogues with sulfonyl chloride or sulfonyl hydrazine to give 5-(1-halo-2-tosyl)vinyluracil nucleoside derivatives has been developed. Nucleophilic substitution of the 5-(β-halovinyl)sulfonyl nucleosides with various nucleophiles have been performed to give highly functionalized 5-vinyl pyrimidine nucleosides via the addition-elimination mechanism. The 5-(β-keto)sulfonyluracil derivative has also been synthesized via the aerobic difunctionalization of 5-ethynyluracil analogue with sulfinic acid in the presence of catalytic amount of pyridine. Silver catalyzed hydroazidation of protected 2'-deoxy-5-ethynyluridine with TMSN3 in the presence of catalytic amount of water to give 5-(α-azidovinyl)uracil nucleoside derivatives was developed. Strain promoted Click reaction of the 5-(α-azidovinyl)uracil with cyclooctyne provide the corresponding fully conjugated triazole product.

Part 1: Transition-metal-catalyzed direct transformations of aromatic C-H bonds are emerging as valuable tools in organic synthesis. These reactions are attractive because of they allow for inherently efficient construction of organic building blocks by minimizing the pre-activation of substrates. Of these processes, direct arylation has recently received much attention due to the importance of the biaryl core in medicinal and materials chemistry. Also, alkyne hydroarylation has garnered interest because it allows for the atom-economical synthesis of functionalized alkenes directly from simple arenes and alkynes. Described in this thesis are number of advancements in these areas. First, palladium catalyzed direct arylation of azine N-oxides using synthetically important aryl triflates is described. Interesting reactivity of aryl triflates compared to aryl bromides was uncovered and exploited in the synthesis of a compound that exhibits antimalarial and antimicrobial activity. Also reported is the efficient, direct arylation enabled (formal) synthesis of six thiophene based organic electronic materials in high yields using simple starting materials. Additionally, the site-selective direct arylation of both sp2 and sp3 sites on azine N-oxide substrates is described. The arylation reactions are carried out in either a divergent manner or a sequential manner and is applied to the synthesis of the natural products, Papaverine and Crykonisine. Mechanistic investigations point towards the intimate involvement of the base in the mechanism of these reactions. Next, the rhodium(III)-catalyzed hydroarylation of internal alkynes is described. Good yields are obtained for a variety of alkynes and arenes with excellent regioselectivity for unsymmetrically substituted alkynes. Mechanistic investigations suggest that this reaction proceeds through arene metalation with the cationic rhodium catalyst, which enables challenging intermolecular reactivity. Part 2: Access to single enantiomer compounds is a fundamental goal in organic chemistry and despite remarkable advances in enantioselective synthesis, their preparation remains a challenge. Kinetic resolution of racemic products is an important method to access enantioenriched compounds, especially when alternative methods are scarce. Described in this thesis is the resolution of tertiary and secondary alcohols, which arise from ketone and aldehyde aldol additions. The method is technically simple, easily scalable, and provides tertiary and secondary alcohols in high enantiomeric ratios. A rationale for the unique reactivity/selectivity associated with (1S,2R)-N-methylephedrine in the resolution is proposed. Organocatalysis is a rapidly developing, powerful field for the construction of enantioenriched organic molecules. Described here is a complimentary class of organocatalysis using simple aldehydes as temporary tethers to perform challenging formally intermolecular reactions at room temperature. This strategy allows for the enantioselective, intermolecular cope-type hydroamination of allylic amines with hydroxyl amines. Also, interesting catalytic reactivity for dichloromethane is revealed.

Palladium-catalyzed reactions for carbon-carbon bond formation have had a significant impact on the field of organic chemistry in recent decades. Illustrative is the 2010 Nobel Prize, awarded for “palladium-catalyzed cross couplings in organic synthesis”, and the numerous applications of these transformations in industrial settings. This thesis describes recent developments in C(sp2)-C(sp3) bond formation, focusing on alkane arylation reactions and arylative dearomatization transformations. In the first part, our contributions to the development of intramolecular C(sp3)-H arylation reactions from aryl chlorides are described (Chapter 2). The use of catalytic quantities of pivalic acid was found to be crucial to observe the desired reactivity. The reactions are highly chemoselective for arylation at primary aliphatic C-H bonds. Theoretical calculations revealed that C-H bond cleavage is facilitated by the formation of an agostic interaction between the palladium centre and a geminal C-H bond. In the following section, the development of an alkane arylation reaction adjacent to amides and sulfonamides is presented (Chapter 3). The mechanism of C(sp3)-H bond cleavage in alkane arylation reactions is also addressed through an in-depth experimental and theoretical mechanistic study. The isolation and characterization of an intermediate in the catalytic cycle, the evaluation of the roles of both carbonate and pivalate bases in reaction mechanism as well as kinetic studies are reported. Our serendipitous discovery of an arylation reaction at cyclopropane methylene C-H bonds is discussed in Chapter 4. Reaction conditions for the conversion of cyclopropylanilines to quinolines/tetrahydroquinolines via one-pot palladium(0)-catalyzed C(sp3)-H arylation with subsequent oxidation/reduction are described. Initial studies are also presented, which suggest that this transformation is mechanistically unique from other Pd catalyzed cyclopropane ring-opening reactions. Preliminary investigations towards the development of an asymmetric alkane arylation reaction are highlighted in Chapter 5. Both chiral carboxylic acid additives and phosphine ligands have been examined in this context. While high yields and enantiomeric excesses were never observed, encouraging results have been obtained and are supported by recent reports from other research groups. Finally, in part two, the use of Pd(0)-catalysis for the intramolecular arylative dearomatization of phenols is presented (Chapter 7). These reactions generate spirocyclohexadienones bearing all-carbon quaternary centres in good to excellent yields. The nature of the base, although not well understood, appears to be crucial for this transformation. Preliminary results in the development of an enantioselective variant of this transformation demonstrate the influence of catalyst activation on levels of enantiomeric excess.

Methane and dinitrogen are abundant precursors to numerous valuable chemicals such as methanol and ammonia, respectively. However, given the robustness of these substrates, catalytically circumventing the high temperatures and pressures required for such transformations has been a challenging task for chemists. In this work, computational studies of various transition metal catalysts for methane C-H activation and N2 activation have been carried out. For methane C-H activation, catalysts of the form LnM=E are studied, where Ln is the supporting ligand (dihydrophosphinoethane or β-diketiminate), E the activating ligand (O, NCH3, NCF3) at which C-H activation takes place, and M the late transition metal (Fe,Co,Ni,Cu). A hydrogen atom abstraction (HAA) / radical rebound (RR) mechanism is assumed for methane functionalization (CH4 à CH3EH). Since the best energetics are found for (β-diket)Ni=O and (β-diket)Cu=O catalysts, with or without CF3 substituents around the supporting ligand periphery, complete methane-to-methanol cycles were studied for such systems, for which N2O was used as oxygen atom transfer (OAT) reagent. Both monometallic and bimetallic OAT pathways are addressed. Monometallic Fe-N2 complexes of various supporting ligands (LnFe-N2) are studied at the beginning of the N2 activation chapter, where the effect of ligand on N2 activation in end-on vs. side-on N2 isomers is discussed. For (β-diket)Fe-N2 complexes, the additional influence of diketiminate donor atom (N(H) vs. S) is briefly addressed. The remainder of the chapter expands upon the treatment of β-diketiminate complexes. First, the activation and relative stabilities of side-bound and end-bound N2 isomers in monometallic ((β-diket)M-N2) and bimetallic ((β-diket)M-N2-M(β-diket)) first row transition metal complexes are addressed. Second, the thermodynamics of H/H+/H- addition to (β-diket)Fe-bound N2, followed by subsequent H additions up to release of ammonia, is discussed, for which two mechanisms (distal and alternating) are considered. Finally, the chapter concludes with partial distal and alternating mechanisms for H addition to N2 in bimetallic (β-diket)Fe-N2-Fe(β-diket) and (β-diket)M-N2-M(β-diket) (M = Ti,V,Fe), respectively.

A CuI fully fluorinated O-donor monodentate alkoxide complex, K[Cu(OC4F9)2] (1), was previously shown to form a trinuclear copper–dioxygen species with a {Cu3(3-O)2} core, TOC4F9, upon reactivity with O2 at low temperature. A significantly expanded kinetic and mechanistic study of TOC4F9 formation is reported using stopped-flow spectroscopy. The TOC4F9 complex performed catalytic oxidase conversion of para-hydroquinone (H2Q) to para-benzoquinone (BQ) and hydroxylation of 2,4-di-tert-butylphenolate (DBP) to catecholate, making TOC4F9 the first tri-copper species to perform tyrosinase (both monooxygenase and oxidase) chemistry. As opposed to 1, when K+ is fully encapsulated in {K(18C6)}[Cu(OC4F9)2] (4), O2 was not reduced under identical conditions. To study the effects of both alkali cation and the degree of encapsulation on reduction of O2, derivative complexes were synthesized with Na+ (16), {Na(DME)}+ (17), {Na(15C5)}+ (18), {K(15C5)}+ (19), {K(15C5)2}+ (20), Cs+ (21), {Cs(18C6)}+ (22), and {Cs(18C6)2}+ (23). Reduction of O2 was found to be encapsulation-dependent, and cation size was also determined to affect the chromophore observed. These results suggest that cation…F/O interactions between the CuI complexes assemble aggregates that are required to form reactive {Cun−O2} species. However, catalytic oxidation of H2Q to BQ and sub-stoichiometric oxidation of DBP to catecholate occurred regardless of whether a {Cun−O2} intermediate was detected, suggesting that a reactive species may self-assemble in the presence of substrate in all complex derivatives unable to reduce O2. A series of heteroleptic mixed phosphine/alkoxide 3d complexes was designed to evaluate PPh3 as a protecting group. Complexes of the form [(Ph3P)2M(OC4F9)2] (M= Fe (24), Co (25), Ni (26), Zn (27)) and [(Ph3P)2M(pinF)] (M= Co (31), Ni (32), Zn (33)) were prepared and characterized, along with related complexes with non-reactive L-donors for comparison, [(DME)Fe(OC4F9)2] (28) and [(Ph3PO)2M(OC4F9)2] (M= Fe (29), Ni (30)). Dimeric [Fe2(-O)(OPPh3)2(OC4F9)4] (36) was isolated after O2 reactivity with 24, and 28 and 29 were able to generate intermediate species capable of both oxidation of H2Q to BQ and oxygen atom transfer of thioanisole to methyl phenyl sulfoxide. The choice of fluorinated ligand influences O2 reactivity with CoII (25, 31), but not for NiII (26, 32). Related dimeric compounds [Co2(pinF)2(THF)4)] (34) and [Zn2(pinF)2(THF)2)] (35) were also isolated.

京都大学 / 0048 / 新制・課程博士 / 博士(工学) / 甲第22455号 / 工博第4716号 / 新制||工||1737(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 中尾 佳亮, 教授 松原 誠二郎, 教授 杉野目 道紀 / 学位規則第4条第1項該当 / Doctor of Philosophy (Engineering) / Kyoto University / DFAM

京都大学 / 0048 / 新制・課程博士 / 博士(工学) / 甲第22663号 / 工博第4747号 / 新制||工||1742(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 村上 正浩, 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

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