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Author:
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ISBN:
Category :
Languages : en
Pages : 360
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Book Description
Rhodium catalyzed asymmetric hydroformylation (AHF) generates chirality and a versatile functional group in a single atom-economic reaction, yet remains underutilized in the synthesis of fine chemicals and pharmaceuticals. Bis-3,4-diazaphospholanes have already been demonstrated as highly selective and active ligands for this process with a range of substrates. However, continued improvements to these ligands expand the scope of substrates, allow for rapid optimization with new substrates, and facilitate the development of industrial-scale processes. This work describes the synthesis of a library of bisdiazaphospholanes, immobilization on solid supports to facilitate recycling, and synthesis of primary phosphines to develop bisdiazaphospholanes containing additional electron withdrawing groups. In order to improve optimization of AHF reactions, libraries of easily synthesized bisdiazaphospholanes are required. A tetraacyl fluoride bisdiazaphospholane was prepared which can be used to generate previously examined as well as previously inaccessible tetracarboxamide bisdiazaphospholanes. This library was applied to the hydroformylation of vinyl acetate, styrene, allyloxy-t-butyldimethylsilane, (E)-1-phenyl-1,3-butadiene, 2,3-dihydrofuran, and 2,5-dihydrofuran. Tertiary carboxamide bisdiazaphospholanes synthesized for this library allowed for AHF of 2,3- and 2,5-dihydrofuran with simultaneously high rates and selectivities. Bisdiazaphospholanes that demonstrated high selectivity were then immobilized on resin supports via the same amide coupling method used to generate the previous ligand library. Bisdiazaphospholanes immobilized on Tentagel resins give selectivities similar to the homogenous catalyst and show similar reactivity trends for styrene and 2,3-dihydrofuran AHF. While the activities of the immobilized catalyst are three to four times slower compared to the homogenous catalyst, they can be recycled without loss of selectivity and minimal rhodium leaching, ultimately leading to higher productivity. The immobilized bisdiazaphospholanes were used in a plug flow reactor with similar selectivity and recyclability as in batch reactors. Attempts to synthesize bisdiazaphospholanes with a fluorinated backbone were carried out using tetrafluorobisphosphinobenzene. The synthesis of tetrafluorobisphosphinobenzene was performed using phenylsilane as a safe alternative to lithium aluminum hydride. Unfortunately, purification of the desired primary phosphine was low yielding and could not be improved. NMR analysis indicates that the desired bisdiazaphospholanes could be generated using standard procedures, but these new ligands have not yet been applied to hydroformylation.
Author:
Publisher:
ISBN:
Category :
Languages : en
Pages : 360
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Book Description
Rhodium catalyzed asymmetric hydroformylation (AHF) generates chirality and a versatile functional group in a single atom-economic reaction, yet remains underutilized in the synthesis of fine chemicals and pharmaceuticals. Bis-3,4-diazaphospholanes have already been demonstrated as highly selective and active ligands for this process with a range of substrates. However, continued improvements to these ligands expand the scope of substrates, allow for rapid optimization with new substrates, and facilitate the development of industrial-scale processes. This work describes the synthesis of a library of bisdiazaphospholanes, immobilization on solid supports to facilitate recycling, and synthesis of primary phosphines to develop bisdiazaphospholanes containing additional electron withdrawing groups. In order to improve optimization of AHF reactions, libraries of easily synthesized bisdiazaphospholanes are required. A tetraacyl fluoride bisdiazaphospholane was prepared which can be used to generate previously examined as well as previously inaccessible tetracarboxamide bisdiazaphospholanes. This library was applied to the hydroformylation of vinyl acetate, styrene, allyloxy-t-butyldimethylsilane, (E)-1-phenyl-1,3-butadiene, 2,3-dihydrofuran, and 2,5-dihydrofuran. Tertiary carboxamide bisdiazaphospholanes synthesized for this library allowed for AHF of 2,3- and 2,5-dihydrofuran with simultaneously high rates and selectivities. Bisdiazaphospholanes that demonstrated high selectivity were then immobilized on resin supports via the same amide coupling method used to generate the previous ligand library. Bisdiazaphospholanes immobilized on Tentagel resins give selectivities similar to the homogenous catalyst and show similar reactivity trends for styrene and 2,3-dihydrofuran AHF. While the activities of the immobilized catalyst are three to four times slower compared to the homogenous catalyst, they can be recycled without loss of selectivity and minimal rhodium leaching, ultimately leading to higher productivity. The immobilized bisdiazaphospholanes were used in a plug flow reactor with similar selectivity and recyclability as in batch reactors. Attempts to synthesize bisdiazaphospholanes with a fluorinated backbone were carried out using tetrafluorobisphosphinobenzene. The synthesis of tetrafluorobisphosphinobenzene was performed using phenylsilane as a safe alternative to lithium aluminum hydride. Unfortunately, purification of the desired primary phosphine was low yielding and could not be improved. NMR analysis indicates that the desired bisdiazaphospholanes could be generated using standard procedures, but these new ligands have not yet been applied to hydroformylation.
Author: Julia Wildt
Publisher:
ISBN:
Category :
Languages : en
Pages : 0
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Book Description
Hydroformylation is one of the largest homogenously catalyzed transformations in industry, leading to important aldehyde product from alkene starting materials. Asymmetric hydroformylation on the other hand is underdeveloped. The challenge is to maintain high regio- and enantioselectivities for the resulting branched aldehyde. Extensive research is performed on the development and synthesis on chelating bisphosphorus ligands to help control the desired selectivities. However, the substrate scope is only limited for any single ligand. With the discovery of the class of bisdiazaphospholane ligands by Landis and coworker, new paths were opened in addressing a broad scope of substrates over the years. The ligand (S,S,S)-BisDiazaPhos represents a state-of-the-art ligand, that can hydroformylate a variety of substrate with fast rates, while maintaining both high regio- and enantioselectivity. This work focuses on the synthesis of novel 3,4-diazaphospholane ligands to expand the existing library and to address new substrate or improve upon existing selectivities. Chapter 3 shows that racemic 2,5-phenyl-and naphthyl-substituted bisdiazaphospholanes, containing the acylhydrazine backbone can be reduced with BH3 to yield alkylhydrazine based bisdiazaphospholanes. These reduced ligands have been tested in the rhodium-catalyzed hydroformylation of different substrate classes. Interestingly, the regioselectivity with the reduced ligands was improved compared to their non-reduced analogues. This improvement is considered to come from the conformational change in the ring structure, where an increased torsion angle within the ring correlates to higher regioselectivities. A steric quadrant model is used to rationalize the improved regioselectivities for the reduced bisdiazaphospholanes. Chapter 4 describes the development of boronate bearing diazaphospholanes as directing or scaffolding ligands for the purpose of intramolecular hydroformylation of the challenging substrate class of allylic and homoallylic alcohols. This concept takes advantage of functional groups that can coordinate covalently to a substrate and datively to a metal center, leading to improved selectivity and reactivity compared to a non-directed transformations. The synthesis of these novel boronate bearing diazaphospholanes is laid out. The directed hydroformylation of allylic substrates was not observed with mono-diazaphospholanes. The synthesis towards chelating bisdiazaphospholane is described and thought to have the potential to gain further insights into the directing effects of bisdiazaphospholane structures.
Author: Maurizio Taddei
Publisher: Springer
ISBN: 3642450598
Category : Science
Languages : en
Pages : 233
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Book Description
The Role of Metals and Ligands in Organic Hydroformylation, by Luca Gonsalvi, Antonella Guerriero, Eric Monflier, Frédéric Hapiot, Maurizio Peruzzini. Hydroformylation in Aqueous Biphasic Media Assisted by Molecular Receptors, by Frédéric Hapiot, Hervé Bricout, Sébastien Tilloy, Eric Monflier. Asymmetric Hydroformylation, by Bernabé F. Perandones, Cyril Godard, Carmen Claver. Domino Reactions Triggered by Hydroformylation, by Elena Petricci, Elena Cini. Rhodium-Catalyzed Hydroformylation in Fused Azapolycycles Synthesis, by Roberta Settambolo. Hydroformylation in Natural Product Synthesis, by Roderick W. Bates, Sivarajan Kasinathan.
Author: Montserrat Diéguez
Publisher: John Wiley & Sons
ISBN: 3527804072
Category : Technology & Engineering
Languages : en
Pages : 431
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Book Description
An important reference for researchers in the field of metal-enzyme hybrid catalysis Artificial Metalloenzymes and MetalloDNAzymes in Catalysis offers a comprehensive review of the most current strategies, developed over recent decades, for the design, synthesis, and optimization of these hybrid catalysts as well as material about their application. The contributors—noted experts in the field—present information on the preparation, characterization, and optimization of artificial metalloenzymes in a timely and authoritative manner. The authors present a thorough examination of this interesting new platform for catalysis that combines the excellent selective recognition/binding properties of enzymes with transition metal catalysts. The text includes information on the various applications of metal-enzyme hybrid catalysts for novel reactions, offers insights into the latest advances in the field, and contains an informative perspective on the future: Explores the development of artificial metalloenzymes, the modern and strongly evolving research field on the verge of industrial application Contains a comprehensive reference to the research area of metal-enzyme hybrid catalysis that has experienced tremendous growth in recent years Includes contributions from leading researchers in the field Shows how this new catalysis combines the selective recognition/binding properties of enzymes with transition metal catalysts Written for catalytic chemists, bioinorganic chemists, biochemists, and organic chemists, Artificial Metalloenzymes and MetalloDNAzymes in Catalysis offers a unique reference to the fundamentals, concepts, applications, and the most recent developments for more efficient and sustainable synthesis.
Author: Piet W.N.M. van Leeuwen
Publisher: Springer Science & Business Media
ISBN: 0306469472
Category : Science
Languages : en
Pages : 291
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Book Description
In the last decade there have been numerous advances in the area of rhodium-catalyzed hydroformylation, such as highly selective catalysts of industrial importance, new insights into mechanisms of the reaction, very selective asymmetric catalysts, in situ characterization and application to organic synthesis. The views on hydroformylation which still prevail in the current textbooks have become obsolete in several respects. Therefore, it was felt timely to collect these advances in a book. The book contains a series of chapters discussing several rhodium systems arranged according to ligand type, including asymmetric ligands, a chapter on applications in organic chemistry, a chapter on modern processes and separations, and a chapter on catalyst preparation and laboratory techniques. This book concentrates on highlights, rather than a concise review mentioning all articles in just one line. The book aims at an audience of advanced students, experts in the field, and scientists from related fields. The didactic approach also makes it useful as a guide for an advanced course.
Author: Carmen Claver
Publisher: Springer
ISBN: 3319666657
Category : Science
Languages : en
Pages : 291
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Book Description
The series Topics in Organometallic Chemistry presents critical overviews of research results in organometallic chemistry. As our understanding of organometallic structure, properties and mechanisms increases, new ways are opened for the design of organometallic compounds and reactions tailored to the needs of such diverse areas as organic synthesis, medical research, biology and materials science. Thus the scope of coverage includes a broad range of topics of pure and applied organometallic chemistry, where new breakthroughs are being achieved that are of significance to a larger scientific audience. The individual volumes of Topics in Organometallic Chemistry are thematic. Review articles are generally invited by the volume editors. All chapters from Topics in Organometallic Chemistry are published OnlineFirst with an individual DOI. In references, Topics in Organometallic Chemistry is abbrev iated as Top Organomet Chem and cited as a journal.
Author: P.A. Chaloner
Publisher: Springer Science & Business Media
ISBN: 9401717915
Category : Science
Languages : en
Pages : 293
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Book Description
Homogeneous hydrogenation is one of the most thoroughly studied fields of homogeneous catalysis. The results of these studies have proved to be most important for an understanding of the underlying principles of the activation of small molecules by transition metal complexes. During the past three decades homogeneous hydrogenation has found widespread application in organic chemistry, including the production of important pharmaceuticals, especially where a sophisticated degree of selectivity is required. This volume presents a general account of the main principles and applications of homogeneous hydrogenation by transition metal complexes. Special attention is devoted to the mechanisms by which these processes occur, and the role of the recently discovered complexes of molecular hydrogen is described. Sources of hydrogen, other than H2, are also considered (transfer hydrogenation). The latest achievements in highly stereoselective hydrogenations have made possible many new applications in organic synthesis. These applications are documented by giving details of the reduction of important unsaturated substrates (alkenes, alkynes, aldehydes and ketones, nitrocompounds, etc.). Hydrogenation in biphasic and phase transfer catalyzed systems is also described. Finally, a discussion of the biochemical routes of H2 activation highlights the similarities and differences in performing hydrogenation in both natural and synthetic systems. For researchers working in the fields of homogeneous catalysis, especially in areas such as pharmaceuticals, plastics and fine chemicals.
Author: Jean-Philippe Goddard
Publisher: John Wiley & Sons
ISBN: 111969504X
Category : Science
Languages : en
Pages : 162
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Book Description
Biphasic Chemistry and The Solvent Case examines recent improvements in reaction conditions, in order to affirm the role of chemistry in the sustainable field. This book shows that those who work within the chemistry industry support limits for the use of toxic or flammable solvents, since it reduces the purifications to simple filtrations. Thanks to commercial scavengers, solid phase syntheses are now available to all. Fluorine biphasic catalysis enables extremely efficient catalyst recycling and has a high applicability potential at the industrial level. This book also reviews the many studies that have shown that water is a solvent of choice for most synthetic reactions. Particular traits can be obtained and the effects on thermodynamics make it possible to operate at lower temperatures, thereby achieving energy savings. Finally the great diversity of application of the reactions without solvents is illustrated.
Author: J. Falbe
Publisher:
ISBN: 9783642674532
Category :
Languages : en
Pages : 484
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Book Description
Author: J. A. McCleverty
Publisher: Newnes
ISBN: 0080913164
Category : Science
Languages : en
Pages : 11845
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Book Description
Comprehensive Coordination Chemistry II (CCC II) is the sequel to what has become a classic in the field, Comprehensive Coordination Chemistry, published in 1987. CCC II builds on the first and surveys new developments authoritatively in over 200 newly comissioned chapters, with an emphasis on current trends in biology, materials science and other areas of contemporary scientific interest.
