The field of metal-catalyzed C–H bond functionalizations is an incredibly vibrant and spans beyond the formations of biaryl motifs. The introduction chapter will cover the mechanistic aspects of the C–H bond functionalization with metal-carboxylate complexes. The mechanistic facets of this reaction will be the main conducting line between the different sections and chapters of the first part of this thesis. In the second chapter, will be described additives that can readily promoted C–H bond arylation of poorly reactive substrates. More specifically, we will revisit the intramolecular direct arylation reaction we will demonstrate the effect of pivalic acid as a co-catalyst by developing milder reaction conditions. In the third chapter we be described experimental and computational studies which suggested that the a single pathway might be involved in the palladium-catalyzed C–H bond functionalization of a wide range of (hetero)arene. Following this we will describe a general set of conditions for the direct arylation of wide range of heteroarenes. Also, we will present two different strategies to selectively and predictably arylate substrates containing multiple functionalizable C–H bonds. In the fourth chapter will be presented our efforts toward the development of new C–H bond functionalization methods in which we could apply our knowledge on the C–H bond cleavage and apply it to the formation of new scaffolds. The development of two new palladium-catalyzed methods were also described. In the fifth chapter, our effort toward the development of ligands to specifically promoted C–H bond cleavage will be presented. In the sixth chapter will be presented the latest results on the study of the mechanism of the C–H bond cleavage combining experimental and computational studies. In part B of this thesis will be presented our strategy toward the total synthesis of ginkgolide C that included two gold(I)-catalyzed reactions as key steps in the preparation of the spiro[4.4]nonane core of this natural product. The first studies on the feasibility of the key steps of the synthesis will be described.

The field of metal-catalyzed C–H bond functionalizations is an incredibly vibrant and spans beyond the formations of biaryl motifs. The introduction chapter will cover the mechanistic aspects of the C–H bond functionalization with metal-carboxylate complexes. The mechanistic facets of this reaction will be the main conducting line between the different sections and chapters of the first part of this thesis. In the second chapter, will be described additives that can readily promoted C–H bond arylation of poorly reactive substrates. More specifically, we will revisit the intramolecular direct arylation reaction we will demonstrate the effect of pivalic acid as a co-catalyst by developing milder reaction conditions. In the third chapter we be described experimental and computational studies which suggested that the a single pathway might be involved in the palladium-catalyzed C–H bond functionalization of a wide range of (hetero)arene. Following this we will describe a general set of conditions for the direct arylation of wide range of heteroarenes. Also, we will present two different strategies to selectively and predictably arylate substrates containing multiple functionalizable C–H bonds. In the fourth chapter will be presented our efforts toward the development of new C–H bond functionalization methods in which we could apply our knowledge on the C–H bond cleavage and apply it to the formation of new scaffolds. The development of two new palladium-catalyzed methods were also described. In the fifth chapter, our effort toward the development of ligands to specifically promoted C–H bond cleavage will be presented. In the sixth chapter will be presented the latest results on the study of the mechanism of the C–H bond cleavage combining experimental and computational studies. In part B of this thesis will be presented our strategy toward the total synthesis of ginkgolide C that included two gold(I)-catalyzed reactions as key steps in the preparation of the spiro[4.4]nonane core of this natural product. The first studies on the feasibility of the key steps of the synthesis will be described.

The field of metal-catalyzed C–H bond functionalizations is an incredibly vibrant and spans beyond the formations of biaryl motifs. The introduction chapter will cover the mechanistic aspects of the C–H bond functionalization with metal-carboxylate complexes. The mechanistic facets of this reaction will be the main conducting line between the different sections and chapters of the first part of this thesis. In the second chapter, will be described additives that can readily promoted C–H bond arylation of poorly reactive substrates. More specifically, we will revisit the intramolecular direct arylation reaction we will demonstrate the effect of pivalic acid as a co-catalyst by developing milder reaction conditions. In the third chapter we be described experimental and computational studies which suggested that the a single pathway might be involved in the palladium-catalyzed C–H bond functionalization of a wide range of (hetero)arene. Following this we will describe a general set of conditions for the direct arylation of wide range of heteroarenes. Also, we will present two different strategies to selectively and predictably arylate substrates containing multiple functionalizable C–H bonds. In the fourth chapter will be presented our efforts toward the development of new C–H bond functionalization methods in which we could apply our knowledge on the C–H bond cleavage and apply it to the formation of new scaffolds. The development of two new palladium-catalyzed methods were also described. In the fifth chapter, our effort toward the development of ligands to specifically promoted C–H bond cleavage will be presented. In the sixth chapter will be presented the latest results on the study of the mechanism of the C–H bond cleavage combining experimental and computational studies. In part B of this thesis will be presented our strategy toward the total synthesis of ginkgolide C that included two gold(I)-catalyzed reactions as key steps in the preparation of the spiro[4.4]nonane core of this natural product. The first studies on the feasibility of the key steps of the synthesis will be described.

Thesis advisor: Masayuki Wasa / Thesis advisor: Amir H. Hoveyda / This dissertation describes the development of cooperative catalyst systems that contain an achiral Lewis acid and a chiral Lewis acid that may have overlapping functions but play their independent roles to promote enantioselective C–C bond formations. Chapter 1 provides a summary of recent advances made in the field of enantioselective cooperative catalysis that served as intellectual foundations for this dissertation research. As it will be discussed in the first chapter, key limitations of cooperative catalysis are: (1) undesirable catalyst deactivation which occurs due to acid/base complexation, (2) requirement for base sensitive pronucleophiles and acid sensitive electrophiles, and (3) poor reaction efficiency. In an effort to overcome these fundamental limitations, we have developed “frustrated” Lewis pair (FLP)-based catalyst systems that consist of potent and sterically encumbered Lewis acids used in pair with bulky N-containing Lewis bases. To demonstrate the potential of the novel FLP catalyst system, we describe our work involving the enantioselective Conia-ene-type cyclization (Chapter 2). In the subsequent chapter (Chapter 3), we discuss the application of the FLP catalysts for enantioselective β-amino C–H functionalization reactions. / Thesis (PhD) — Boston College, 2021. / Submitted to: Boston College. Graduate School of Arts and Sciences. / Discipline: Chemistry.

Thesis advisor: Masayuki Wasa / This dissertation describes the development of novel catalyst systems that could promote the regio- and enantioselective transformations of C-H bonds contained in N-alkylamines and ethers through Lewis acid-mediated hydride abstraction processes. The progress made in C-H functionalization of N-alkylamines and ethers that served as the intellectual foundation of this dissertation research are summarized in Chapter 1. Despite notable advances, the development of broadly applicable, enantioselective, and catalytic protocols to functionalize C-H bonds in N-alkylamines and ethers with high regio- and stereo-selectivity was regarded as an unsolved problem when we started this dissertation research. In an effort to overcome these fundamental limitations, we first identified a B(C6F5)3/Cu-PyBOX cooperative catalyst system for the enantioselective conversion of a-amino C-H bonds through the generation of an iminium by (F5C6)3B-catalyzed hydride abstraction process (Chapter 2). We then envisioned that in situ generated iminium ions could be further deprotonated to furnish an enamine intermediate, which may react with electrophilic species for a-amino C-H functionalization. The design and development of such a catalyst system were discussed in Chapter 3. Finally, we disclose enantioselective Cu–BOX-catalyzed hetero Diels-Alder reactions of enol ethers generated through Ph3C+-mediated oxidation of alkyl ethers. (Chapter 4). / Thesis (PhD) — Boston College, 2022. / Submitted to: Boston College. Graduate School of Arts and Sciences. / Discipline: Chemistry.

No description available.

Indiana University-Purdue University Indianapolis (IUPUI) / Alkyl radicals are powerful intermediates for the generation of carbon-carbon bonds, which play an indispensable role in the synthesis of natural products, pharmaceuticals, and pesticides. Traditionally, there are two main methods for the generation of alkyl radicals. The first is C-H bond functionalization via hydrogen-atom-transfer (HAT). HAT processes have been used as an effective approach for selectively activating C-H bonds via radical pathways. The other strategy to explore the generation of alkyl radicals is C-X bond functionalization via halogen-atom-transfer (XAT). Alkyl halides are one of the largest classes of building blocks in synthesis and they can be obtained from the corresponding alcohols. The most straightforward and effective way to form such alkyl radicals is the direct homolytic cleavage of C-X bonds. In past decades, photoredox catalysis has emerged as a powerful and greener tool for the synthesis of radicals under mild reaction conditions, which has brought tremendous attention. Although remarkable success has been made in this field, some methods still require costly transition metal catalysts or toxic reagents. Herein, we display a series of visible light-induced approaches under transition-metal free conditions or using earth-abundant metals. These novel photo-induced transformations and corresponding mechanistic work will be discussed in the following order: We will first present our work on metal-free visible-light-promoted C(sp3)-H functionalization of aliphatic cyclic ethers using trace O2. This reaction uses a trace amount of aerobic oxygen as the sole green oxidant under blue light at room temperature to achieve the synthesis of sulfone and phosphate derivatives in good to excellent yields using cyclic ethers and vinyl sulfones. Then, we report on a photo-induced C(sp3)-H chalcogenation of amide derivatives and ethers via a ligand-to-metal charge-transfer. This reaction converts secondary and tertiary amides, sulfonamides, and carbamates into the corresponding amido-N,S-acetal derivatives in good yields, using an earth abundant metal catalyst under mild conditions. Finally, we present a photoredox polyfluoroarylation of alkyl halides via halogen atom transfer. This method converts primary, secondary, and tertiary unactivated abundant alkyl halides into the corresponding polyfluoroaryl compounds in good yields and has good functional group compatibility.

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.

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.