Applied Asymmetric Hydroformylation with Rhodium-bisdiazaphospholane Catalysts PDF Download
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Languages : en
Pages : 298
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Book Description
The conversion of olefins into aldehydes by hydroformylation with rhodium catalysts is one of the largest homogeneously catalyzed industrial reactions, producing millions of tons of linear aldehydes per year. However, the production of chiral, branched aldehydes via asymmetric hydroformylation (AHF) remains underutilized in synthesis. To improve the application of rhodium BisDiazaphos catalyzed AHF, high selectivity for previously uninvestigated disubstituted olefins including enol esters and enamides is demonstrated, which yield more complex [alpha]-functionalized aldehyde building blocks. Additionally, process-scale asymmetric hydroformylation to yield chiral, enantioenriched aldehyde feedstocks has not yet been demonstrated. In collaboration with Eli Lilly, asymmetric hydroformylation in a research scale flow reactor is realized through the development of a flow synthesis of naproxen. To support scale-up of asymmetric hydroformylation technologies the synthesis of bisdiazaphospholane ligands is re-examined to optimize the cost of the material and synthesis on a larger scale is demonstrated. Access to enantiopure ligand via classical resolution in place of preparative SFC chromatography has also been developed, and will improve accessibility to selective AHF catalysts. Finally, the direct observation of catalytic intermediates and rate information in asymmetric hydroformylation by circulating high-pressure NMR will be described.
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ISBN:
Category :
Languages : en
Pages : 298
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Book Description
The conversion of olefins into aldehydes by hydroformylation with rhodium catalysts is one of the largest homogeneously catalyzed industrial reactions, producing millions of tons of linear aldehydes per year. However, the production of chiral, branched aldehydes via asymmetric hydroformylation (AHF) remains underutilized in synthesis. To improve the application of rhodium BisDiazaphos catalyzed AHF, high selectivity for previously uninvestigated disubstituted olefins including enol esters and enamides is demonstrated, which yield more complex [alpha]-functionalized aldehyde building blocks. Additionally, process-scale asymmetric hydroformylation to yield chiral, enantioenriched aldehyde feedstocks has not yet been demonstrated. In collaboration with Eli Lilly, asymmetric hydroformylation in a research scale flow reactor is realized through the development of a flow synthesis of naproxen. To support scale-up of asymmetric hydroformylation technologies the synthesis of bisdiazaphospholane ligands is re-examined to optimize the cost of the material and synthesis on a larger scale is demonstrated. Access to enantiopure ligand via classical resolution in place of preparative SFC chromatography has also been developed, and will improve accessibility to selective AHF catalysts. Finally, the direct observation of catalytic intermediates and rate information in asymmetric hydroformylation by circulating high-pressure NMR will be described.
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.
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Languages : en
Pages : 0
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Hydroformylation is a large-scale commodity process in the synthesis of aldehydes from alkene, carbon monoxide and hydrogen gas starting materials; in contrast, asymmetric hydroformylation (AHF) is underutilized in the synthesis of chiral aldehydes. Because rhodium-catalyzed hydroformylation exhibits perfect atom-economy, high turnover numbers, and fast rates, this is a desirable reaction in synthesis of branched chiral aldehydes. Challenges in AHF include control of selectivity (chemo-, regio-, and enantio- ), slow rates of reaction, and a limited substrate scope. Currently, only a handful of chiral phosphorus-containing ligands exhibit state-of-the-art rates of reaction and high levels of enantioselectivity in rhodium-catalyzed hydroformylation for a broad range of substrates; even less of these have found applications in complex molecule and natural product synthesis. This work describes the synthesis of a bis-3,4-diazaphospholane ligand library, hydroformylation of O-functionalized alkenes, and application with Wittig olefination in the synthesis of complex organic molecules. A library of bis-3,4-diazaphospholanes ligands was generated by varying the steric bulk in the secondary coordination sphere and applied to the hydroformylation of three terminal alkenes. Styrene exhibited modest variations in regio- and enantioselectivity, whereas, vinyl acetate and allyloxy-t-butyldimethylsilane exhibited fairly minor changes. Enantioselective hydroformylation of allyl ethers with bisdiazaphospholane ligands yield synthetically useful building blocks for organic synthesis; one prominent example, chiral "Roche aldehyde" can be accessed from inexpensive allyl alcohol. AHF of 5-grams of an allyl silyl ether and a protected acrolein demonstrate scalable syntheses of chiral building blocks relevant for natural product synthesis. One-pot asymmetric hydroformylation-Wittig olefinations (AHF-WO) is performed with various alkenes using Rh-bisdiazaphospholane catalysts resulting in [alpha, beta]-unsaturated carbonyl products. In these experiments multiple AHF-WO iterations demonstrate the utility of the synthesis of complex molecules with various functionalities, multiple carbon-carbon double bonds, and stereocenters. Overall this body of work promotes the use of bisdiazaphospholane ligands for enantioselective hydroformylation and organic synthesis
Author: Bradley R. Jones
Publisher:
ISBN:
Category :
Languages : en
Pages : 394
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Book Description
The synthesis of complex organic molecules requires efficient routes for carbon-carbon bond formation. Selective, atom economic processes are highly desired for these transformations. One such reaction, hydroformylation, the formation of aldehydes by addition of CO and H2 across an alkene, fits these characteristics. Linear selective hydroformylation to generate alkyl aldehydes is one of the largest homogeneously catalyzed reactions performed industrially. However, asymmetric hydroformylation (AHF), generating chiral branched aldehydes is comparatively underdeveloped. Bisdiazaphospholane (BDP) ligands developed by the Landis group are highly regio- and enantioselective for AHF when paired with a rhodium metal center, but the limited availability and inconvenient synthesis have limited their use. An improved, scalable route to enantiopure BDP ligands featuring resolution of diastereomeric salts is described. This new route delivers BDP ligands with higher yield and purity while avoiding the use of chromatography. The potential industrial use of these ligands and AHF for the synthesis of fine chemicals is demonstrated through the development of AHF in flow, in collaboration with Eli Lilly. Additionally, synthetic applications of the aldehydes produced via AHF are expanded through new hydroacylation methodology. This approach utilizes the same functional groups which promote selective hydroformylation as directing groups for hydroacylation.
Author: Clarence E. Clark
Publisher:
ISBN:
Category :
Languages : en
Pages : 132
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Category :
Languages : en
Pages : 360
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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.
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ISBN:
Category :
Languages : en
Pages : 160
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Rhodium-catalyzed hydroformylation, which converts alkenes to aldehydes via the addition of H2 and CO, is among the largest-volume industrial applications of homogeneous catalysis. However, fundamental questions concerning the origins of regio- and enantioselectivity in hydroformylation remain unanswered because key reaction intermediates have never been characterized. The rhodium-bis(diazaphospholane) complexes introduced by Landis and coworkers in 2005 are highly active and offer exceptional regio- and stereoselectivity. In this work, we report the interception and characterization of catalyst species using these complexes, including rhodium-alkyl complexes, which have never been characterized for any catalyst system, and rhodium-acyl complexes. By examining the kinetic and thermodynamic parameters of these species for the substrates styrene, vinyl acetate, allyl cyanide, and 1-octene, and comparing those results to catalytic selectivity, we demonstrate that the kinetic behavior of the acyl complexes can be considered a reasonable model for catalytic selectivity, offering an unprecedented window into this important but poorly-understood reaction.
Author: Julia Wildt
Publisher:
ISBN:
Category :
Languages : en
Pages : 0
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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: Xiao-Feng Wu
Publisher: John Wiley & Sons
ISBN: 3527831894
Category : Science
Languages : en
Pages : 1780
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Book Description
The Chemical Transformations of C1 Compounds A comprehensive exploration of one-carbon molecule transformations The chemistry of one-carbon molecules has recently gained significant prominence as the world transitions away from a petroleum-based economy to a more sustainable one. In The Chemical Transformations of C1 Compounds, an accomplished team of chemists delivers an in-depth overview of recent developments in the field of single-carbon chemistry. The three-volume book covers all major C1 sources, including carbon monoxide, carbon dioxide, methane, methanol, formic acid, formaldehyde, carbenes, C1 halides, and organometallics. The editors have included resources discussing the main reactions and transformations into feedstock chemicals of each of the major C1 compounds reviewed in dedicated chapters. Readers will discover cutting-edge material on organic transformations with MeNO2, DMF, DCM, methyl organometallic reagents, CCl4, CHCl3, and CHBr3, as well as recent achievements in cyanation reactions via cross-coupling. The book also offers: Thorough introductions to chemical transformations of CH4, methods of CH4 activation, chemical transformations of CH3OH and synthesis alkenes from CH3OH Comprehensive explorations of the carbonylation of MeOH, CH2O in organic synthesis, organic transformations of HCO2H, and hydrogen generation from HCO2H Practical discussions of the carbonylation of unsaturated bonds with heterogeneous and homogeneous catalysts, as well as the carbonylation of C(sp2)-X bonds and C(sp3)-X bonds In-depth examinations of carbonylative C-H bond activation and radical carbonylation Perfect for organic and catalytic chemists, The Chemical Transformations of C1 Compounds is also an ideal resource for industrial chemists, chemical engineers, and practitioners at energy supply companies.
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Publisher: Newnes
ISBN: 008097743X
Category : Science
Languages : en
Pages : 9815
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Book Description
The second edition of Comprehensive Organic Synthesis—winner of the 2015 PROSE Award for Multivolume Reference/Science from the Association of American Publishers—builds upon the highly respected first edition in drawing together the new common themes that underlie the many disparate areas of organic chemistry. These themes support effective and efficient synthetic strategies, thus providing a comprehensive overview of this important discipline. Fully revised and updated, this new set forms an essential reference work for all those seeking information on the solution of synthetic problems, whether they are experienced practitioners or chemists whose major interests lie outside organic synthesis. In addition, synthetic chemists requiring the essential facts in new areas, as well as students completely new to the field, will find Comprehensive Organic Synthesis, Second Edition, Nine Volume Set an invaluable source, providing an authoritative overview of core concepts. Winner of the 2015 PROSE Award for Multivolume Reference/Science from the Association of American Publishers Contains more than170 articles across nine volumes, including detailed analysis of core topics such as bonds, oxidation, and reduction Includes more than10,000 schemes and images Fully revised and updated; important growth areas—including combinatorial chemistry, new technological, industrial, and green chemistry developments—are covered extensively
