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Author: Ryan Sawatzky Publisher: ISBN: Category : Languages : en Pages : 0
Book Description
Homogeneous organometallic complexes have become an indispensable tool as they are employed as catalysts for a large number of chemical transformations. Ancillary ligands, organic molecules that bind to the metal center, are critical for fine tuning the performance of these catalysts. The initial portion of this thesis describes a comparative survey of several state-of-the-art ligands for Pd catalyzed C-O cross-coupling reactions. As part of this survey two sets of conditions are employed: reactions carried out at 90 °C, using 1 mol % Pd, and room temperature reactions, using 7 mol % Pd. In these comparisons, it was found that Rockphos was the ligand of choice for reactions at room temperature, as well for electron rich electrophiles. The Josiphos variant, CyPF-tBu, was the optimal ligand for reactions at elevated temperatures, as well as for activated electrophiles. Many ligands that have found use in Pd chemistry have been repurposed for use in Ni catalysis. While this an effective strategy, it is not necessarily ideal. The bisphosphine PAd-Dalphos has been tailored for Ni catalyzed monoarylation of ammonia, and primary amines. Here, ammonium, methylamine, and ethylamine salts are successfully used as cross-coupling partners employing microwave heating. High yielding reactions, utilizing as little as 1 mol % Ni can be completed in as little as 5 minutes under these conditions. In an effort to establish trends of reactivity in Ni catalysis, the complex (DPEphos)Ni(mesityl)Br was developed for both C-N, C-C cross-coupling reactions. This complex was first established in the cross-coupling of secondary amines, and azoles with activated aryl chlorides. The observation of PhB(OH)2 required as a catalyst activator lead to the development of this complex as a catalyst for C-C cross-coupling using unstable 5-membered heterocyclic boronic acids for challenging biheteroaryl formation. Here reactions conducted at room temperature were found to be comparable to the previous state-of-the-art Ni catalysis. In addition, 3-pyridinyl-boronic acids were also successfully employed. While the scope of reactivity with such challenging substrates was modest, the work herein represents a step forward as only a small handful of examples exist for Ni catalyzed reactions.
Author: Ryan Sawatzky Publisher: ISBN: Category : Languages : en Pages : 0
Book Description
Homogeneous organometallic complexes have become an indispensable tool as they are employed as catalysts for a large number of chemical transformations. Ancillary ligands, organic molecules that bind to the metal center, are critical for fine tuning the performance of these catalysts. The initial portion of this thesis describes a comparative survey of several state-of-the-art ligands for Pd catalyzed C-O cross-coupling reactions. As part of this survey two sets of conditions are employed: reactions carried out at 90 °C, using 1 mol % Pd, and room temperature reactions, using 7 mol % Pd. In these comparisons, it was found that Rockphos was the ligand of choice for reactions at room temperature, as well for electron rich electrophiles. The Josiphos variant, CyPF-tBu, was the optimal ligand for reactions at elevated temperatures, as well as for activated electrophiles. Many ligands that have found use in Pd chemistry have been repurposed for use in Ni catalysis. While this an effective strategy, it is not necessarily ideal. The bisphosphine PAd-Dalphos has been tailored for Ni catalyzed monoarylation of ammonia, and primary amines. Here, ammonium, methylamine, and ethylamine salts are successfully used as cross-coupling partners employing microwave heating. High yielding reactions, utilizing as little as 1 mol % Ni can be completed in as little as 5 minutes under these conditions. In an effort to establish trends of reactivity in Ni catalysis, the complex (DPEphos)Ni(mesityl)Br was developed for both C-N, C-C cross-coupling reactions. This complex was first established in the cross-coupling of secondary amines, and azoles with activated aryl chlorides. The observation of PhB(OH)2 required as a catalyst activator lead to the development of this complex as a catalyst for C-C cross-coupling using unstable 5-membered heterocyclic boronic acids for challenging biheteroaryl formation. Here reactions conducted at room temperature were found to be comparable to the previous state-of-the-art Ni catalysis. In addition, 3-pyridinyl-boronic acids were also successfully employed. While the scope of reactivity with such challenging substrates was modest, the work herein represents a step forward as only a small handful of examples exist for Ni catalyzed reactions.
Author: Joseph Michael Dennis (Jr.) Publisher: ISBN: Category : Languages : en Pages : 549
Book Description
Chapter 1: Breaking the Base Barrier: An Electron-Deficient Palladium Catalyst Enables the Use of a Common Soluble Base in C-N Coupling Due to the low intrinsic acidity of amines, palladium-catalyzed C-N cross-coupling plagued continuously by the necessity to employ strong, inorganic, or insoluble bases. To surmount the many Due to the low intrinsic acidity of amines, palladium-catalyzed C-N crosscoupling has been practical obstacles associated with these reagents, we utilized a commercially available dialkyl triarylmonophosphine-supported palladium catalyst that facilitates a broad range of C-N coupling reactions in the presence of weak, soluble bases. The mild and general reaction conditions show extraordinary tolerance for even highly base-sensitive functional groups. Additionally, insightful heteronuclear NMR studies using −15N-labeled amine complexes provide evidence for the key acidifying effect of the cationic palladium center. Chapter 2: Pd-Catalyzed C-N Coupling Reactions Facilitated by Organic Bases: Mechanistic Investigation Leads to Enhanced Reactivity in the Arylation of Weakly Binding Amines The ability to use soluble organic amine bases in Pd-catalyzed C-N cross-coupling reactions has provided a long-awaited solution to the many issues associated with employing traditional, heterogeneous reaction conditions. However, little is known about the precise function of these bases in the catalytic cycle or about the effect of variations in base structure on catalyst reactivity. We used 19F NMR to analyze the kinetic behavior of C-N coupling reactions facilitated by different organic bases. In the case of aniline coupling reactions employing DBU, the resting state was a DBU-bound oxidative addition complex, LPd(DBU)(Ar)X, and the reaction was found to be inhibited by base. Generally, however, depending on the binding properties of the chosen organic base, increasing the concentration of the base can have a positive or negative influence on the reaction rate. Furthermore, the electronic nature of the aryl triflate employed in the reaction directly affects the reaction rate. The fastest reaction rates were observed with electronically neutral aryl triflates, while the slowest were observed with highly electron-rich and electrondeficient substrates. We propose a model in which the turnover-limiting step of the catalytic cycle is dependent on the relative nucleophilicity of the base, compared to that of the amine. This hypothesis guided the discovery of new reaction conditions for the coupling of weakly binding amines, including secondary aryl amines, which were unreactive nucleophiles in our original protocol. Chapter 3: Use of a Droplet Platform to Optimize Pd-Catalyzed C-N Coupling Reactions Promoted by Organic Bases Recent advances in Pd-catalyzed carbon-nitrogen cross-coupling have enabled the use of soluble organic bases instead of insoluble or strong inorganic bases that are traditionally employed. The single-phase nature of these reaction conditions facilitates their implementation in continuous flow systems, high-throughput optimization platforms, and large-scale applications. In this work, we utilized an automated microfluidic optimization platform to determine optimal reaction conditions for the couplings of an aryl triflate with four types of commonly employed amine nucleophiles: anilines, amides, primary aliphatic amines, and secondary aliphatic amines. By analyzing trends in catalyst reactivity across different reaction temperatures, base strengths, and base concentrations, we have developed a set of general recommendations for Pd-catalyzed crosscoupling reactions involving organic bases. The optimization algorithm determined that the catalyst supported by the dialkyltriarylmonophosphine ligand AlPhos was the most active in the coupling of each amine nucleophile. Furthermore, our automated optimization revealed that the phosphazene base BTTP can be used to facilitate the coupling of secondary alkylamines and aryl triflates. Chapter 4: The Quest for the Ideal Base: Rational Design of a Nickel Precatalyst Enables Mild, Homogeneous C-N Cross-Coupling Palladium-catalyzed amination reactions using soluble organic bases have provided a solution to the many issues associated with heterogeneous reaction conditions. Still, homogeneous C-N crosscoupling approaches cannot yet employ bases as weak and economical as trialkylamines. Furthermore, organic base-mediated methods have not been developed for Ni(0/II) catalysis, despite some advantages of such systems over analogous Pd-based catalysts. We designed a new air-stable and easily prepared Ni(II) precatalyst bearing an electron-deficient bidentate phosphine ligand that enables the cross-coupling of aryl triflates with aryl amines using triethylamine (TEA) as base. The method is tolerant of sterically-congested coupling partners, as well as those bearing base- and nucleophile-sensitive functional groups. With the aid of density functional theory (DFT) calculations, we determined that the electron-deficient auxiliary ligands decrease both the pK[subscript a] of the Ni-bound amine and the barrier to reductive elimination from the resultant Ni(II)-amido complex. Moreover, we determined that precluding Lewis acid-base complexation between the Ni catalyst and the base, due to steric factors, is important for avoiding catalyst inhibition.
Author: José Pérez Sestelo Publisher: MDPI ISBN: 3039435671 Category : Science Languages : en Pages : 234
Book Description
In this Special Issue, recent advances in cross-coupling reactions are presented in the form of original research articles, reviews, and short communications. These contributions cover different topics in this area, including novel coupling reactions, reaction conditions, synthetic alternatives, metal ligands, and applications for new pharmaceutical compounds and organic materials. In particular, the reviews deal with methodologies such as the synthesis of diarylketones through palladium catalysis and the most relevant examples of Suzuki–Miyaura and Buchwald–Hartwig coupling reactions in the synthesis of bioactive compounds. The synthetic utility of cross-coupling reactions for the synthesis of medium-size rings and the utility of Stille and Suzuki coupling reactions for the synthesis of new molecular machines based on sterically hindered anthracenyl trypticenyl units are also summarized. The original research articles present the synthesis of 2-alkynylpyrrols by inverse Sonogashira coupling and the synthesis of indoles under oxidative dearomative cross-dehydrogenative conditions. The efficient combination of iridium-catalyzed C–H borylation of aryl halides with the Sonogashira coupling and a sequential iridium-catalyzed borylation of NH-free pyrroles followed by a Suzuki–Miyaura reaction are included. The synthesis of aryl propionic acids, a common structural motif in medicinal chemistry, and the synthesis of new organic dyes are also covered.
Author: Árpád Molnár Publisher: John Wiley & Sons ISBN: 3527648305 Category : Science Languages : en Pages : 531
Book Description
This handbook and ready reference brings together all significant issues of practical importance in selected topics discussing recent significant achievements for interested readers in one single volume. While covering homogeneous and heterogeneous catalysis, the text is unique in focusing on such important aspects as using different reaction media, microwave techniques or catalyst recycling. It also provides a comprehensive treatment of key issues of modern-day coupling reactions having emerged and matured in recent years and emphasizes those topics that show potential for future development, such as continuous flow systems, water as a reaction medium, and catalyst immobilization, among others. With its inclusion of large-scale applications in the pharmaceutical industry, this will equally be of great interest to industrial chemists. From the contents * Palladium-Catalyzed Cross-Coupling Reactions - A General Introduction * High-turnover Heterogeneous Palladium Catalysts in Coupling Reactions: the Case of Pd Loaded on Dealuminated Y Zeolites Palladium-Catalyzed Coupling Reactions with Magnetically Separable Nanocatalysts * The Use of Ordered Porous Solids as Support Materials in Palladium-Catalyzed Cross-Coupling Reactions * Coupling Reactions Induced by Polymer-Supported Catalysts * Coupling Reactions in Ionic Liquids * Cross-Coupling Reactions in Aqueous Media * Microwave-Assisted Synthesis in C-C and C-Heteroatom Coupling Reactions * Catalyst Recycling in Palladium-Catalyzed Carbon-Carbon Coupling Reactions * Nature of the True Catalytic Species in Carbon-Carbon Coupling Reactions with * Heterogeneous Palladium Precatalysts * Coupling Reactions in Continuous Flow Systems * Large-Scale Applications of Palladium-Catalyzed Couplings in the Pharmaceutical Industry
Author: Armin de Meijere Publisher: John Wiley & Sons ISBN: 3527655603 Category : Science Languages : en Pages : 1640
Book Description
This three volume book is the follow-up handbook to the bestselling volume "Metal-Catalyzed Cross-Coupling Reactions", the definitive reference in the field. In line with the enormous developments in this area, this is not a new edition, but rather a new book in three volumes with over 50% more content. This new content includes C-H activation, shifting the focus away from typical cross-coupling reactions, while those topics and chapters found in de Meijere/Diederich's book have been updated and expanded. With its highly experienced editor team and the list of authors reading like an international Who's-Who in the field, this work will be of great interest to every synthetic chemist working in academia and industry.
Author: François Diederich Publisher: John Wiley & Sons ISBN: 3527612203 Category : Science Languages : de Pages : 540
Book Description
Carbon-carbon bond forming reactions are arguably the most important processes in chemistry, as they represent key steps in the building of complex molecules from simple precursors. Among these reactions, metal-catalyzed cross-coupling reactions are extensively employed in a wide range of areas of preparative organic chemistry, ranging from the synthesis of complex natural products, to supramolecular chemistry, and materials science. In this work, a dozen internationally renowned experts and leaders in the field bring the reader up to date by documenting and critically analyzing current developments and uses of metal-catalyzed cross-coupling reactions. A particularly attractive and useful feature, that enhances the practical value of this monograph, is the inclusion of key synthetic protocols, in experimental format, chosen for broad utility and application. This practice-oriented book can offer the practitioner short cuts to ensure they remain up-to-date with the latest developments.
Author: Yoshinao Tamaru Publisher: John Wiley & Sons ISBN: 3527604235 Category : Science Languages : en Pages : 346
Book Description
Organonickel chemistry plays an increasingly important role in organic chemistry, and interest in this topic is now just as keen as in organopalladium chemistry. While there are numerous, very successful books on the latter, a book specializing in organonickel chemistry is long overdue. Edited by one of the leading experts in the field, this volume covers the many discoveries made over the past 30 years, and previously scattered throughout the literature. Active researchers working at the forefront of organonickel chemistry provide a comprehensive review of the topic, including cross-coupling reactions, asymmetric synthesis and heterogeneous catalysis reaction types. A must-have for both organometallic chemists and synthetic organic chemists.
Author: Martin Oestreich Publisher: John Wiley & Sons ISBN: 9780470716069 Category : Science Languages : en Pages : 608
Book Description
Exploring the importance of Richard F. Heck’s carbon coupling reaction, this book highlights the subject of the 2010 Nobel Prize in Chemistry for palladium-catalyzed cross couplings in organic synthesis, and includes a foreword from Nobel Prize winner Richard F. Heck. The Mizoroki-Heck reaction is a palladium-catalyzed carbon–carbon bond forming process which is widely used in organic and organometallic synthesis. It has seen increasing use in the past decade as chemists look for strategies enabling the controlled construction of complex carbon skeletons. The Mizoroki-Heck Reaction is the first dedicated volume on this important reaction, including topics on: mechanisms of the Mizoroki-Heck reaction intermolecular Mizoroki-Heck reactions focus on regioselectivity and product outcome in organic synthesis waste-minimized Mizoroki-Heck reactions intramolecular Mizoroki-Heck reactions formation of heterocycles chelation-controlled Mizoroki-Heck reactions the Mizoroki-Heck reaction in domino processes oxidative heck-type reactions (Fujiwara-Moritani reactions) Mizoroki-Heck reactions with metals other than palladium ligand design for intermolecular asymmetric Mizoroki-Heck reactions intramolecular enantioselective Mizoroki-Heck reactions desymmetrizing Mizoroki-Heck reactions applications in combinatorial and solid phase syntheses, and the development of modern solvent systems and reaction techniques the asymmetric intramolecular Mizoroki-Heck reaction in natural product total synthesis Several chapters are devoted to asymmetric Heck reactions with particular focus on the construction of otherwise difficult-to-obtain sterically congested tertiary and quaternary carbons. Industrial and academic applications are highlighted in the final section. The Mizoroki-Heck Reaction will find a place on the bookshelves of any organic or organometallic chemist. “I am convinced that this book will rapidly become the most important reference text for research chemists in academia and industry who seek orientation in the rapidly growing and – for the layman – confusing field described as the “’Mizoroki–Heck reaction’.” (Synthesis, March 2010)
Author: Aaron George Johnson Publisher: ISBN: 9781321846461 Category : Languages : en Pages : 246
Book Description
Transition metal catalyzed cross-coupling reactions have become a staple of organic synthesis and are frequently the most practical strategy for the preparation of medicinal agents and fine chemicals. Catalysts based on the precious metal palladium are commonly used in cross-coupling reactions. Replacing palladium catalysts with nickel catalysts is an active area of research as such advances present significant benefits including increasing the sustainability of transformations and new mechanisms for control of stereochemistry in the construction of Csp-Csp3 bonds. In Chapter 1, a stereospecific nickel-catalyzed cross-coupling reaction of secondary benzylic ethers with a variety of aliphatic and aryl Grignard reagents is presented. The method is highly stereospecific and proceeds with inversion at the benzylic carbon. Products prepared by this method were subject to biological testing, and a thiophene-containing product was shown to selectively inhibit the growth of MCF-7 breast cancer cells. In Chapter 2, mechanistic studies that provide insight into the mechanism of oxidative addition as well as the mechanisms of major side reactions, hydrogenolysis and Îø-hydride elimination, are presented. Experiments presented provide evidence that the mechanisms of cross-coupling, hydrogenolysis, and B-hydride elimination reactions all include a step of oxidative addition with inversion at the benzylic center. Hydrogenolysis was also shown to be stereospecific, proceeding with overall inversion at the stereogenic center. In Chapter 3, the application of nickel-catalyzed cross-coupling reactions to the synthesis of either enantiomer of a bioactive triaryl methane from a single enantiomer of a precursor alcohol is presented. In the key cross-coupling step a Kumada protocol allows for cross-coupling with inversion at the benzylic carbon, while a Suzuki reaction allows for cross-coupling with retention.
Author: John F. Hartwig Publisher: ISBN: Category : Science Languages : en Pages : 1172
Book Description
Based on Collman et al.'s best-selling classic book, Principles and Applications of Organotransition Metal Chemistry, Hartwig's text consists of new or thoroughly updated and restructured chapters and provides an in-depth view into mechanism, reaction scope, and applications. It covers the most important developments in the field over the last twenty years with great clarity with a selective, but thorough and authoritative coverage of the fundamentals of organometallic chemistry, the elementary reactions of these complexes, and many catalytic processes occurring through organometallic intermediates, making this the Organotransition Metal Chemistry text for a new generation of scientists.
Author: Ryan Sawatzky
Author: Ryan Sawatzky
Author: Joseph Michael Dennis (Jr.)
Author: José Pérez Sestelo
Author: Árpád Molnár
Author: Armin de Meijere
Author: François Diederich
Author: Yoshinao Tamaru
Author: Martin Oestreich
Author: Aaron George Johnson
Author: John F. Hartwig