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2024 | Book

Palladium-Catalyzed Mechanochemical Cross-Coupling Reactions

Author: Tamae Seo

Publisher: Springer Nature Singapore

Book Series : Springer Theses

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About this book

In this thesis, the author developed cross-coupling reactions that proceed in the solid state without using organic solvents, utilizing a mechanochemical synthesis method using a ball mill. Compared to conventional solution systems, the reactions realized a drastic reduction of chemical waste, a drastic acceleration of chemical reactions, and efficient transformations of insoluble compounds. The thesis demonstrates that mechanochemical synthesis method has the potential to revolutionize organic synthesis. Readers can learn not only about mechanochemical synthesis but also about new reactions and syntheses of new compounds that could not be obtained under solution conditions. Recently, mechanochemical synthesis has become increasingly popular among a wide range of researchers as an environmentally friendly and highly efficient method, so this thesis has a timely publication.

Table of Contents

Frontmatter
Chapter 1. General Introduction
Abstract
In the past two decades, mechanochemistry has become increasingly popular among a wide range of researchers as an environmentally friendly and highly efficient method. This method has been extensively exploited in material science, polymer chemistry, and inorganic and organic synthesis.
Tamae Seo
Chapter 2. Olefin-Accelerated Solid-State C–N Cross-Coupling Using Mechanochemistry
Abstract
Palladium-catalyzed cross-coupling reactions are one of the most powerful and versatile methods to synthesize a wide range of complex functionalized molecules. However, the development of solid-state cross-coupling reactions remains extremely limited. Here, the author reported a rational strategy that provides a general entry to palladium-catalyzed Buchwald-Hartwig cross-coupling reactions in the solid state. The key finding of this study is that olefin additives can act as efficient molecular dispersants for the palladium-based catalyst in solid-state media to facilitate the challenging solid-state cross-coupling. Beyond the immediate utility of this protocol, this strategy could inspire the development of industrially attractive solvent-free palladium-catalyzed cross-coupling processes for other valuable synthetic targets.
Tamae Seo
Chapter 3. Solid-State Suzuki–Miyaura Cross-Coupling Reaction Using Mechanochemistry
Abstract
The Suzuki–Miyaura cross-coupling reaction is one of the most reliable methods for the construction of carbon–carbon bonds in solution. However, examples for the corresponding solid-state cross-coupling reactions remain scarce. Herein, the author reports the first broadly applicable mechanochemical protocol for a solid-state palladium-catalyzed organoboron cross-coupling reaction using an olefin additive. Compared to previous studies, the newly developed protocol shows a substantially broadened substrate scope. The author’s mechanistic data suggest that olefin additives might act as dispersants for the palladium-based catalyst to suppress higher aggregation of the nanoparticles, and also as stabilizer for the active monomeric Pd(0) species, thus facilitating these challenging solid-state C–C bond-forming cross-coupling reactions.
Tamae Seo
Chapter 4. Tackling Solubility Issues in Organic Synthesis: Solid-State Cross-Coupling of Insoluble Aryl Halides
Abstract
Conventional organic synthesis generally relies on the use of liquid organic solvents to dissolve the reactants. Therefore, reactions of sparingly soluble or insoluble substrates are challenging and often ineffective. The development of a solvent-independent solid-state approach that overcomes this longstanding solubility issue would provide innovative synthetic solutions and access to new areas of chemical space. Here, the author reports extremely fast and highly efficient solid-state palladium-catalyzed Suzuki–Miyaura cross-coupling reactions via a high-temperature ball-milling technique. This solid-state protocol enables the highly efficient cross-couplings of insoluble aryl halides with large polyaromatic structures that are barely reactive under conventional solution-based conditions. Notably, the author discovered a new luminescent organic material with a strong red emission. This material was prepared via the solid-state coupling of Pigment violet 23, a compound that has so far not been involved in molecular transformations due to its extremely low solubility. This study thus provides a practical method for accessing unexplored areas of chemical space through molecular transformations of insoluble organic compounds that cannot be carried out by any other approach.
Tamae Seo
Chapter 5. Solid-State Cross-Coupling Reactions of Insoluble Aryl Halides Under Polymer-Assisted Grinding Conditions
Abstract
In this study, polymer-assisted grinding (POLAG), a ball milling technique based on the use of polymer additives, was applied to mechanochemical solid-state Suzuki–Miyaura cross-coupling reactions of insoluble aryl halides. The author found that the efficiency of this challenging solid-state cross-coupling was successfully improved by the addition of polytetrafluoroethylene (PTFE) as a POLAG additive under high-temperature ball-milling conditions. My results suggest that POLAG is a promising approach for controlling the reactivity of insoluble substrates that are barely reactive under conventional solution-based conditions.
Tamae Seo
Chapter 6. Mechanochemistry-Directed Ligand Design: Development of a High-Performance Phosphine Ligand for Palladium-Catalyzed Mechanochemical Organoboron Cross-Coupling
Abstract
Mechanochemical synthesis with transition-metal catalysts has attracted significant attention because of its numerous advantages, including reduced solvent waste, shorter reaction times, and the avoidance of problems posed by low solubility of starting materials. However, despite the fact that mechanochemical reaction environment is largely different from that of homogeneous solution systems, transition-metal catalysts originally developed for solution-based conditions have also been diverted to mechanochemical reactions without molecular-level devices suitable for mechanochemistry, which limits further development of more efficient mechanochemical cross-coupling processes. Here the author reports the conceptually distinct, mechanochemistry-directed ligand design for palladium-catalyzed Suzuki–Miyaura cross-coupling reaction using ball milling. The ligand development was guided by the experimental observation of catalyst deactivation associated with aggregation of palladium species, which was particularly prominent in solid-state reactions. By introducing a flexible polyethylene glycol (PEG) chain into the ligand backbone, the author found that phosphine-ligated palladium (0) species could be efficiently immobilized in the fluid amorphous phase created by the PEG chains, preventing the catalyst kneading into the crystalline solid phase and the undesired aggregation-induced catalyst deactivation. This new mechanochemistry-directed catalytic system showed high catalytic activity at near room temperature for the reactions of solid polyaromatic substrates that usually require elevated temperature when previous catalysts with ligands commonly used in solution reactions (e.g., SPhos) were employed. The present study provides important perspectives for the rational design of high-performance transition-metal catalysts that potentially inspire the development of industrially attractive, solvent-less mechanochemical cross-coupling technologies.
Tamae Seo
Chapter 7. Mechanochemical Monoarylation of Dihaloarenes Enabled by In-Situ Crystallization
Abstract
Palladium-catalyzed Suzuki–Miyaura cross-coupling reactions of liquid, unbiased dibromoarenes under mechanochemical conditions selectively afford the monoarylated products. The lower reactivity of the crystalline monoarylated products compared to the liquid starting materials should be attributed predominantly to the low diffusion efficiency of the former in the reaction mixture, which results in selective monoarylation. The present study sheds light on a novel approach using in-situ phase transitions in solids to design selective organic transformations that are difficult to achieve vis conventional solution-based synthesis.
Tamae Seo
Chapter 8. Dual Nickel(II)/Mechanoredox Catalysis: Mechanical-Force-Driven Aryl-Amination Reactions Using Ball Milling and Piezoelectric Materials
Abstract
The combination of a nickel(II) catalyst and a mechanoredox catalyst under ball-milling conditions promotes mechanical-force-driven C–N cross-coupling reactions. In this nickel(II)/mechanoredox cocatalyst system, the modulation of the oxidation state of the nickel center, induced by piezoelectricity, is used to facilitate a highly efficient arylamination reaction, which is characterized by a broad substrate scope, an inexpensive combination of catalysts (NiBr2 and BaTiO3), short reaction times, and an almost negligible quantity of solvents. Moreover, this reaction can be readily up-scaled to the multi-gram scale, and all synthetic operations can be carried out under atmospheric conditions without the need for complicated reaction set-ups. Furthermore, this force-induced system is suitable for excitation-energy-accepting molecules and poorly soluble polyaromatic substrates that are incompatible with solution-based nickel(II)/photoredox cocatalysts.
Tamae Seo
Metadata
Title
Palladium-Catalyzed Mechanochemical Cross-Coupling Reactions
Author
Tamae Seo
Copyright Year
2024
Publisher
Springer Nature Singapore
Electronic ISBN
978-981-9719-91-4
Print ISBN
978-981-9719-90-7
DOI
https://doi.org/10.1007/978-981-97-1991-4