Download or read book Palladium Catalyzed C H Functionalization Studies Toward Ginkgolide C written by David Lapointe and published by LAP Lambert Academic Publishing. This book was released on 2012-06-01 with total page 320 pages. Available in PDF, EPUB and Kindle. Book excerpt: The field of metal-catalyzed C H bond functionalizations is an incredibly vibrant and spans beyond the formations of biaryl motifs. The mechanistic aspects of the C H bond functionalization with metal-carboxylate complexes are highlighted. The role of additives, such as pivalic acid, is demonstrated with poorly reactive substrates. A chapter describes experimental and computational studies which suggested that a single pathway might be involved in the palladium-catalyzed C H bond functionalization of a wide range of (hetero)arenes. Afterward a general set of conditions are developed to form biaryls by direct arylation with a wide range of heteroarenes of various complexity level. The development of two new Pd-catalyzed methods based on our knowledge on the C H bond cleavage are apply to the formation of new scaffolds. Efforts toward the development of ligands to specifically promoted C H bond cleavage are presented. Lastly, most recent results on the study of the mechanism of the C H bond cleavage combining experimental and computational studies are discussed. In the second part of the thesis are presented our strategy toward the synthesis of ginkgolide C using gold catalysis.

Download or read book Part A written by David Lapointe and published by . This book was released on 2012 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Strategies for Palladium Catalyzed Non directed and Directed C bond H Bond Functionalization written by Anant R. Kapdi and published by Elsevier. This book was released on 2017-05-23 with total page 502 pages. Available in PDF, EPUB and Kindle. Book excerpt: Strategies for Palladium-Catalyzed Non-directed and Directed C-H Bond Functionalization portrays the complete scope of these two aspects of C-H bond functionalization in a single volume for the first time. Featured topics include the influence of palladacyclic systems in C-H bond functionalization (need for newer catalytic systems for better efficiency), mechanistic aspect of the functionalization strategies leading to better systems, and applications of these methodologies to natural product synthesis and material synthesis. Addresses the involvement of catalytic systems (palladacycles) for better functionalization of (hetero)arenes to emphasize the need for developing better, more selective systems Covers the use of powerful mechanistic tools for understanding and assisting the development of better functionalization strategies Discusses the finer aspects of C-H bond functionalization, such as control of regioselectivity with or without directing groups Includes a chapter detailing the synthesis of naturally occurring molecules or functional molecules via both pathways for assessing the applicability of the functionalization strategies

Download or read book Palladium and Nickel Catalyzed Transformations Forming Functionalized Heterocycles written by Hyung Yoon and published by Springer Nature. This book was released on 2020-09-02 with total page 236 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book presents Pd- and Ni-catalyzed transformations generating functionalized heterocycles. Transition metal catalysis is at the forefront of synthetic organic chemistry since it offers new and powerful methods to forge carbon–carbon bonds in high atom- and step-economy. In Chapter 1, the author describes a Pd- and Ni-catalyzed cycloisomerization of aryl iodides to alkyl iodides, known as carboiodination. In the context of the Pd-catalyzed variant, the chapter explores the production of enantioenriched carboxamides through diastereoselective Pd-catalyzed carboiodination. It then discusses Ni-catalyzed reactions to generate oxindoles and an enantioselective variant employing a dual ligand system. Chapter 2 introduces readers to a Pd-catalyzed diastereoselective anion-capture cascade. It also examines diastereoselective Pd-catalyzed aryl cyanation to synthesize alkyl nitriles, a method that generates high yields of borylated chromans as a single diastereomer, and highlights its synthetic utility. Lastly, Chapter 3 presents a Pd-catalyzed domino process harnessing carbopalladation, C–H activation and π-system insertion (benzynes and alkynes) to generate spirocycles. It also describes the mechanistic studies performed on these reactions.

Download or read book Weak Coordination as a Powerful Means for Developing Useful Palladium II catalyzed C H Activation Reactions written by Tian-Sheng Mei and published by . This book was released on 2011 with total page 846 pages. Available in PDF, EPUB and Kindle. Book excerpt: Achieving direct and selective functionalization of carbon-hydrogen (C-H) bonds to give carbon-carbon (C-C) or carbon-heteroatom (C-Y) bonds is a significant and long-standing goal in chemistry. C-H bonds are attractive reaction partners because they are ubiquitous in organic molecules. Thus, C-H functionalization methods could potentially expedite the synthesis of target molecules by providing new disconnections in retrosynthetic analysis. Among the numerous methods to affect this transformation, palladium-catalyzed C-H functionalization is one of most promising methods to construct C-C and C-Y bonds in term of versatile reactivity. The major challenges of palladium-catalyzed C-H functionalization are developing reactions that work with common and useful structural motifs and discovering new transformation, such as C-N or C-F bond formation. This thesis explores palladium-catalyzed C-H bond functionalization with substrates containing simple functional groups such as carboxylic acids and triflamides, which direct C-H cleavage through weak coordination with the metal catalyst. Chapter one introduces different types of C-H bond functionalization and focuses on Pd(II)/Pd(IV) catalysis. Chapter two covers Pd-catalyzed C-H iodination of arene carboxylic acids enabled by the discovery of coutercation-promoted C-H activation. Weak coordination has also been found to enable versatile reactivity of simple arene carboxylic acids. Chapter three focuses on the development of practical and useful C-H fluorination using triflamide as a weakly coordinating directing group that can be easily manipulated to a wide range of useful and common aryl halides. Chapter four describes applications of bystanding F+ oxidants to promote selective C-N reductive elimination in Pd(II)/Pd(IV) catalysis.

Download or read book Palladium Catalyzed C H Functionalization of Amine Derivatives and Its Application in Total Synthesis written by Wen-Liang Jia and published by . This book was released on 2021 with total page 162 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Pt 1 written by Kelvin Siang Lin Chan and published by . This book was released on 2015 with total page 582 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Chelation assisted Palladium catalyzed Activation of C H Bonds written by Ramesh Giri and published by . This book was released on 2009 with total page 1280 pages. Available in PDF, EPUB and Kindle. Book excerpt: Carbon-hydrogen (C-H) bonds are ubiquitous in organic molecules. Utilization of such abundant chemical moieties as functional group equivalents could shorten route to synthetic targets and provide chemists with new disconnections in retrosynthesis. As such regio- and stereoselective functionalization of unactivated C-H bonds has remained one of the major challenges in organic chemistry. The majority of the transition metals have been rigorously examined for their efficacy in transforming unactivated C-H bonds (pKa >35) into useful functional groups or into C-C bonds. Among those metals, palladium is particularly effective in activating both aromatic (sp2) and aliphatic (sp3) C-H bonds. This thesis explores the reactivity of palladium catalysts in both of these areas. The research herein was conducted using directing groups for C-H cleavage with special focus on utilizing simple functionality such as carboxylic acids. Chapter one details different types of directing groups and their utility in a variety of reactions. Chapters two and three contain details of research on C-heteroatom (C-I and C-O) and C-C bond formation, respectively, with palladium acetate as a catalyst. The iodination and acetoxylation reactions proceed under mild conditions and moderate to excellent levels of diastereoselectivity (up to 99.9%) have been observed with both sp2 and sp3 C-H bonds using oxazoline as the directing group. Mechanistic investigations have been carried out in order to understand the high level of stereoselection and, in this process, a number of palladacycle intermediates have been characterized by X-ray crystallography which led us to assign the absolute stereochemistry of C-H activation. Moreover, the iodination protocol could also be extended to prepare diiodides as intermediates for cyclopropanation which provides a new disconnection approach to construct cyclopropanes. Chapter two discusses C-C bond formation via cross-coupling reactions with organoboron reagents and carbon monoxide using the carboxylic acids as the directing group. Detailed mechanistic investigation along with characterization of intermediate palladacycle formed from sodium toluate have revealed an unprecendented directing ability of carboxylate groups in which the carbonyl oxygen, rather than the O-anion, directs palladium for C-H cleavage.

Download or read book Palladium Catalyzed C H Functionalization written by Zafar Saeed Qureshi and published by . This book was released on 2016 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Intramolecular Direct Functionalization of Cyclopropanes Via Silver Mediated Palladium Catalysis written by Carolyn L. Ladd and published by . This book was released on 2013 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book S O ligand promoted Palladium catalyzed C H Functionalization of Anisole and Aniline Derivatives written by Verena Sukowski and published by . This book was released on 2024 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: "The present PhD thesis deals with the exciting and rapidly evolving field of non-directed C−H functionalization, a groundbreaking approach revolutionizing modern organic synthesis. Traditional synthetic chemistry has heavily relied on prefunctionalization strategies, impeding synthetic efficiency and atom economy. Direct C−H functionalization offers a transformative method for forming C−C and C−X bonds directly from nonfunctionalized substrates, overcoming limitations posed by prefunctionalization. However, challenges such as low reactivity of C−H bonds and selectivity issues persist. The thesis comprises several chapters focusing on the development of synthetic methodologies to achieve precise control over the site-selectivity of C−H functionalization reactions in anisole and aniline derivatives. The catalytic activity of the Pd/S,O-ligand catalyst, particularly in combination with norbornene mediators, is explored. In Chapter 2, a methodology for C−H olefination of anisole derivatives is detailed, emphasizing the importance of ligand modification and solvent selection. Chapter 3 introduces a catalytic system for meta-C−H arylation of aryl ethers, demonstrating superior performance compared to existing systems. Chapter 4 presents the first general and efficient meta-C−H arylation of non-directed aniline derivatives via cooperative catalysis with a palladium–S,O-ligand–norbornene system. Chapter 5 optimizes meta-C−H methylation of non-directed aromatic amines, expanding the scope of late-stage methylation methodologies. Chapter 6 investigates the role of silver salts in Pd/S,O-ligand/NBE catalyzed meta-C−H arylation, providing insights into the kinetics and revealing silver's dual function as a halide scavenger and a promoter of oxidative addition. The thesis contributes significantly to advancing non-directed C−H functionalization, offering new synthetic strategies with broad applications in organic synthesis."--

Download or read book Iron and Palladium Catalyzed C H Functionalization written by Wei Han and published by . This book was released on 2011 with total page 254 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Palladium Catacyzed Carbonylative Approaches to Acyl Electrophiles Using Ligand Effects Or Visible Light written by Yi Liu and published by . This book was released on 2021 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: "Transition metal catalyzed carbonylation reactions have been broadly exploited for the synthesis of carbonyl-containing products. A versatile version of these are palladium-catalyzed carbonylative coupling reactions of organic halides and nucleophiles. However, one drawback to this chemistry is the low electrophilic reactivity of the palladium-acyl intermediates in reaction, which severely limits the scope of nucleophiles that can be employed in carbonylations. This thesis describes studies to address this challenge by the formation of potent acyl electrophiles via metal-catalyzed carbonylations, and their use with non-classical carbonylation nucleophiles. In chapter 2, we demonstrate how the correctly ligated palladium catalyst can be used to create potent acyl-pyridinium electrophiles via the carbonylation of aryl or vinyl triflates, and use these for in situ (hetero)arene C-H bond functionalization. The reaction was catalyzed by a Xantphos-coordinated palladium catalyst, and the bidentate and large-bite-angle ligand is believed to balance the activation of the strong C(sp2)-OTf bonds with the reductive elimination of reactive N-acyl-pyridinium electrophiles. The pyridine employed not only leads to the formation of the acyl-pyridinium salt electrophile, but its structure can be used to modulate selectivity in arene C-H functionalization. Overall, this offers a carbonylative method to form diaryl ketones, [alpha],[beta]-unsaturated ketones, and polycyclic ketones using a broad range of aryl- or vinyl- triflates and (hetero)arenes. Chapter 3 describes an extension of the work in chapter 2, where simple lithium chloride rather than the specialized trifluoromethyl- or methoxy-substituted pyridine can be used as the additive for the palladium catalyzed carbonylative coupling of aryl or vinyl triflates and heteroarenes to form ketones. Mechanistic studies suggest the reaction proceeds by the catalytic generation of acid chloride electrophiles for functionalization of electron-rich heterocycles.A limitation to the carbonylative generation of acyl electrophiles noted above is the need to use aryl- or vinyl-(pseudo)halides as reagents. The association of carbon monoxide to the catalyst severely inhibits oxidative addition reactions, and blocks the use of less reactive substrates such as alkyl halides. In chapter 4, we design a strategy to address these challenges using visible light excitation of palladium. This has opened an approach to perform the carbonylation of diverse array of aryl- and even alkyl-halides and from these build-up acid chlorides with the ability to reaction with various nucleophiles. Mechanistic studies suggest the reaction proceeds via a unique combination of photoevents, where the photoexcitation of Pd(0) induces electron transfer with the organic halide to favor oxidative addition, while the photoexcitation of the Pd(II) intermediate leads to Pd-acyl bond scission and the ultimate reductive elimination of acid chloride electrophiles. While the results in chapter 4 expand the variety of products available from carbonylation, the formation of acid chlorides as reaction products (rather than intermediates) is usually not possible. The latter can be attributed to the high reactivity of acid chlorides, which can lead to their rapid re-addition to the palladium catalyst and either inhibit the reaction or lead to their slow decomposition. In chapter 5, we developed a method to address these limits via the synthesis of less easily reduced acyl fluorides. In this case, mechanistic studies suggest visible light favored oxidative addition to Pd(0) is coupled with rapid ligand driven reductive elimination of the acyl fluoride product, which does not re-add to the Pd(0) once formed. By driving these two reverse steps with different inputs, this has offered a general platform to access acyl fluoride electrophiles, and from these synthesize complex, highly functionalized carbonyl-containing products"--

Download or read book Palladium catalyzed C H Bond Functionalization of Heterocycles and Amines written by Enrico Tapire Nadres and published by . This book was released on 2012 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Palladium-catalyzed functionalization of C-H bonds is becoming an important synthetic tool that allows the preparation of desired substances in fewer steps and higher yields compared to traditional synthetic routes. The C-H bonds can be directly converted to C-C or C-heteroatom bonds. However, the ubiquity of C-H bonds in organic compounds can lead to problems in chemo- and regioselectivity. In heterocycles, the control of regioselectivity of the reaction is governed by the difference in acidity of the heterocyclic ring C-H bonds. An economical method for the arylation of C-H bonds of pyrroles and furans by aryl chlorides was developed. The method employs a palladium acetate catalyst, 2-(dicyclohexylphosphino)biphenyl ligand, and an inorganic base. Electron-rich, electron-poor, and heterocyclic aryl chloride coupling partners can be used and arylated heterocycles are obtained in moderate to good yields. The functionalization of sp2 and sp3 C-H bonds can be promoted by the use of directing groups that coordinate the Pd catalyst and activate the desired C-H functionalities. Use of Pd(OAc)2 in conjunction with cesium acetate or potassium carbonate bases allows functionalization of sp2 and sp3 C-H bonds in amides possessing picolinic acid directing group. Stoichiometric silver additive is not required in contrast with previously published procedure. Arylations are effective for sp2 as well as primary and secondary sp3 C-H bonds. Alkylations of sp2 C-H bonds are successful in most cases. Both primary and secondary alkyl iodides are reactive but secondary alkyl iodides afford low yields. Alkylation of sp2 C-H bonds is low yielding and the reaction requires further optimization. Alkyl and aryl iodides as well as benzyl bromides are reactive. Aryl and alkyl bromides afford no product. Direct conversion of C-H bonds to C-N bonds was also developed. Pd-catalyzed method for pyrrolidine, indoline, and isoindoline formation by cyclization via C-H/N-H coupling is presented. The method employs a picolinamide directing group, PhI(OAc)2 oxidant, and toluene solvent at 80-120 °C. Cyclization is effective for sp2 as well as aliphatic and benzylic sp3 C-H bonds.

Download or read book Palladium Catalyzed C sp2 C sp3 Bond Formation written by Sophie Rousseaux and published by . This book was released on 2012 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: 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.

Download or read book Oxidative Palladium II catalyzed Arene C H Bond Functionalization and Progress Towards the Total Synthesis of 6 Deoxyerythronolide B written by Nadine Borduas and published by . This book was released on 2012 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Synthesis and Elaboration of Heterocycles Via Palladium catalyzed C H Functionalization written by Maria Gerelle and published by . This book was released on 2012 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Chapter 1 is a brief literature review of the most recent progress in the area of C-H functionalization via palladium catalysis. This covers the functionalization of electron deficient arenes and heterocycles with alkenyl and alkyl halides both using inter- and intra-molecular reactions. The chapter also contains an overview of recent work from the Willis group. Chapter 2 presents the functionalization of electron deficient arenes and alkenyl bromides using palladium catalysis (Scheme 1), as well as the use of statistical analysis software for optimizing the cross-coupling reaction. Scheme 1: Functionalization of electron deficient arenes using palladium catalysis Chapter 3 describes the cross-coupling of substituted benzoxazoles, benzothiazole and benzimidazole with a range of alkenyl iodides using palladium catalysis (Scheme 2). The reaction can tolerate both (E) and (Z) disubstituted alkenes and tri-substituted alkenyl iodides, with retention of the double bond geometry. 1 x =0, S, NMe - 14 examples 25-99% yield i Scheme 2: Cross-coupling using benzoxazoles, benzothiazole and benzimidazole with alkenyl iodides Chapter 4 details the synthesis of sultams via an intramolecular functionalization using palladium catalysis. The chapter covers the optimization of the starting material synthesis as well as the cross-coupling reaction. We can access the sulfonamides from cyc1ohexenone and were able to incorporate a large range of substitution patterns (Scheme 3). Scheme 3: Synthesis ofsultams from cyclohexenone Finally, Chapter 5 contains all the experimental details, general considerations and compound data. All the NMR spectra of novel compounds can be found in the appendix. 2.