Rhodium-catalyzed Asymmetric Hydroformylation of Alkenes Using Diazaphospholane Ligands and Application with Wittig Olefination PDF Download
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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
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Languages : en
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Book Description
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: 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: Julia Wildt
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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: Jorge H. Torres King
Publisher:
ISBN:
Category :
Languages : en
Pages : 174
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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.
Author: Christine Le
Publisher:
ISBN:
Category :
Languages : en
Pages : 0
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Book Description
Atom-economical addition reactions to unsaturated carbonâ carbon bonds represent a powerful class of transformations in organic chemistry, since a great deal of molecular complexity can be generated from simple starting materials. Highly regio- and stereoselective processes have been made possible through the use of transition metal catalysts, alongside specialized ancillary ligands and in combination with rational substrate design. One area of research in the Lautens group involves the transition metal catalyzed asymmetric ring opening (ARO) of strained alkenes, which provides access to enantioenriched carbocyclic frameworks. Although a variety of coupling partners have been applied in this transformation, the use of soft carbon nucleophiles remains limited in scope. The first chapter describes a rhodium(I)-catalyzed ARO of meso-oxabicyclic alkenes using silyl enol ethers and ketene acetals. In analogy to the Mukaiyama aldol reaction, a novel silyl migration occurs, enabling an in situ protection of the chiral alcohols obtained. Developing new reactivity from Heck-type carbopalladation processes represents another research interest in the Lautens group. Oxidative addition into a carbonâ halogen bond constitutes the first step of nearly all palladium(0)-catalyzed cross-couplings. Conversely, reductive elimination from palladium(II) to yield an organohalide product represents a rare and often thermodynamically unfavoured process. The next two chapters address challenges in the synthesis of vinyl halides using palladium(0) catalysis via the intramolecular carbohalogenation and chlorocarbamoylation of alkynes. During our investigations, we discovered that the steric bulk of both the substrate and the phosphine ligand play an important role in promoting the desired reactivity. Mechanistic insight has been gained through combined experimental and computational studies, which implicate a palladium-catalyzed stereoisomerization in both of these transformations. Under certain conditions, we demonstrate that highly stereoselective trans-additions to alkynes can be achieved, which illustrates that specific substrate/catalyst combinations can override the inherent cis-selectivity in carbometallations. In the fourth chapter, a formal palladium(II)-catalyzed alkyne chlorocarbamoylation reaction is presented, which provides access to medicinally relevant methylene oxindole scaffolds. In contrast to the analogous protocol using palladium(0) catalysts, the reaction is initiated by an alkyne chloropalladation step, followed by intramolecular cross-coupling with a carbamoyl chloride. Experimental and computational studies provide insight into the mechanism of this reaction.
Author: Avery L. Watkins
Publisher:
ISBN:
Category :
Languages : en
Pages : 134
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Author: P. Andrew Evans
Publisher: John Wiley & Sons
ISBN: 352760409X
Category : Science
Languages : en
Pages : 496
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Book Description
Rhodium has proven to be an extremely useful metal due to its ability to catalyze an array of synthetic transformations, with quite often-unique selectivity. Hydrogenation, C-H activation, allylic substitution, and numerous other reactions are catalyzed by this metal, which presumably accounts for the dramatic increase in the number of articles that have recently emerged on the topic. P. Andrew Evans, the editor of this much-needed book, has assembled an internationally renowned team to present the first comprehensive coverage of this important area. The book features contributions from leaders in the field of rhodium-catalyzed reactions, and thereby provides a detailed account of the most current developments, including: Rhodium-Catalyzed Asymmetric Hydrogenation (Zhang) Rhodium-Catalyzed Hydroborations and Related Reactions (Brown) Rhodium-Catalyzed Asymmetric Addition of Organometallic Reagents to Electron Deficient Olefins (Hayashi) Recent Advances in Rhodium(I)-Catalyzed Asymmetric Olefin Isomerization and Hydroacylation Reactions (Fu) Stereoselective Rhodium(I)-Catalyzed Hydroformylation and Silylformylation Reactions and Their Application to Organic Synthesis (Leighton) Carbon-Carbon Bond-Forming Reactions Starting from Rh-H or Rh-Si Species (Matsuda) Rhodium(I)-Catalyzed Cycloisomerization and Cyclotrimerization Reactions (Ojima) The Rhodium(I)-Catalyzed Alder-ene Reaction (Brummond) Rhodium-Catalyzed Nucleophilic Ring Cleaving Reactions of Allylic Ethers and Amines (Fagnou) Rhodium(I)-Catalyzed Allylic Substitution Reactions and their Applications to Target Directed Synthesis (Evans) Rhodium(I)-Catalyzed [2+2+1] and [4+1] Carbocyclization Reactions (Jeong) Rhodium(I)-Catalyzed [4+2] and [4+2+2] Carbocyclizations (Robinson) Rhodium(I)-Catalyzed [5+2], [6+2], and [5+2+1] Cycloadditions: New Reactions for Organic Synthesis (Wender) Rhodium(II)-Stabilized Carbenoids Containing both Donor and Acceptor Substituents (Davies) Chiral Dirhodium(II)Carboxamidates for Asymmetric Cyclopropanation and Carbon-Hydrogen Insertion Reactions (Doyle) Cyclopentane Construction by Rhodium(II)-Mediated Intramolecular C-H Insertion (Taber) Rhodium(II)-Catalyzed Oxidative Amination (DuBois) Rearrangement Processes of Oxonium and Ammonium Ylides Formed by Rhodium(II)-Catalyzed Carbene-Transfer (West) Rhodium(II)-Catalyzed 1,3-Dipolar Cycloaddition Reactions (Austin) "Modern Rhodium-Catalyzed Organic Reactions" is an essential reference text for researchers at all levels in the general area of organic chemistry. This book provides an invaluable overview of the most significant developments in this important area of research, and will no doubt be an essential text for researchers at academic institutions and professionals at pharmaceutical/agrochemical companies.
Author: Beihan Wang
Publisher:
ISBN:
Category : Alkenes
Languages : en
Pages : 102
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Author:
Publisher:
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.
