Nickel-catalyzed Asymmetric Cross-couplings of Secondary Allylic Chlorides and Planar-chiral Compounds in Asymmetric Synthesis PDF Download
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Author: Sunghee Son
Publisher:
ISBN:
Category :
Languages : en
Pages : 185
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Book Description
In Part I, nickel-catalyzed asymmetric carbon-carbon bond-forming reactions are described. A nickel/Pybox system effectively catalyzes regio- and enantioselective cross-couplings between racemic secondary allylic chlorides and readily available alkylzinc halides. This method is applied to generate two stereo centers in a formal total synthesis of fluvirucinine A1. In Part II, the use of planar-chiral compounds as ligands or catalysts in organic synthesis is described. A C2-symmetric planar-chiral bipyridine is an efficient ligand for copper-catalyzed asymmetric [4+1]-cycloadditions between enones and diazoacetates to form 2,3-dihydrofurans. The highly substituted dihydrofurans are not only obtained in good stereoselectivity but also readily converted to other useful molecules. This method is applied to the first catalytic enantioselective synthesis of a deoxy-C-nucleoside. The synthesis of new C2-symmetric planar-chiral catalysts is described. The diastereoslective functionalization of ferrocene using a chiral directing group enables the formation of a number of amines in enantiopure form. These catalysts are tested as several asymmetric catalysts.
Author: Sunghee Son
Publisher:
ISBN:
Category :
Languages : en
Pages : 185
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Book Description
In Part I, nickel-catalyzed asymmetric carbon-carbon bond-forming reactions are described. A nickel/Pybox system effectively catalyzes regio- and enantioselective cross-couplings between racemic secondary allylic chlorides and readily available alkylzinc halides. This method is applied to generate two stereo centers in a formal total synthesis of fluvirucinine A1. In Part II, the use of planar-chiral compounds as ligands or catalysts in organic synthesis is described. A C2-symmetric planar-chiral bipyridine is an efficient ligand for copper-catalyzed asymmetric [4+1]-cycloadditions between enones and diazoacetates to form 2,3-dihydrofurans. The highly substituted dihydrofurans are not only obtained in good stereoselectivity but also readily converted to other useful molecules. This method is applied to the first catalytic enantioselective synthesis of a deoxy-C-nucleoside. The synthesis of new C2-symmetric planar-chiral catalysts is described. The diastereoslective functionalization of ferrocene using a chiral directing group enables the formation of a number of amines in enantiopure form. These catalysts are tested as several asymmetric catalysts.
Author: Junwon Choi (Ph. D.)
Publisher:
ISBN:
Category :
Languages : en
Pages : 361
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Book Description
Chapter 1 describes the development of three nickel-catalyzed asymmetric Negishi cross-couplings of secondary alkyl electrophiles via a stereoconvergent process. In Section 1.1, asymmetric Negishi arylations and alkenylations of [alpha]-bromonitriles with arylzinc and alkenylzinc reagents are achieved using a nickel/bis(oxazoline) catalyst. Section 1.2 describes stereoconvergent cross-couplings of secondary unactivated alkyl electrophiles, specifically, Negishi arylations and alkenylations of [alpha]-bromosulfonamides and abromosulfones with arylzinc reagents and alkenylzirconium reagents, respectively. Section 1.3 details progress toward asymmetric cross-couplings between [alpha]-haloboronate esters and alkylzinc reagents using a nickel/diamine catalyst. Chapter 2 describes the development of photoinduced, copper-catalyzed C-N couplings between N-heterocycles and aryl halides. In particular, a variety of N-heterocycles, such as indoles, benzimidazoles, imidazoles, and carbazoles, undergo Ullmann couplings under mild conditions (room temperature) with an inexpensive catalyst (Cul, without an added ligand).
Author: Buck L. H. Taylor
Publisher:
ISBN: 9781267652379
Category :
Languages : en
Pages : 171
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Book Description
Transition-metal catalyzed cross-coupling reactions are powerful methods for the synthesis of natural products and medicinal compounds. Cross-coupling reactions of secondary alkyl electrophiles are currently more challenging than those of aryl or vinyl halides, but these reactions enable the construction of tertiary stereogenic centers with control of configuration. Several methods have been reported for the stereoconvergent cross-coupling of alkyl halides using chiral nickel catalysts. Herein, we report the development of a stereospecific cross-coupling reaction of enantioenriched benzylic ethers using achiral nickel catalysts. We initially performed mechanistic studies to determine the stereochemical course of established nickel-catalyzed cross-coupling reactions. A deuterium-labeled alkylborane reagent was used to establish that transmetalation from boron to nickel occurs with retention of configuration. In addition, these studies establish that alkylnickel intermediates are stereochemically stable under these cross-coupling conditions. A stereospecific cross-coupling reaction of benzylic ethers with alkyl Grignard reagents has been developed. Enantioenriched benzylic ethers, derivatives of easily synthesized chiral secondary alcohols, undergo cross-coupling with high enantiospecificity using an achiral nickel catalyst. The method was applied to the asymmetric synthesis of a biologically active diarylethane, a common structural motif in medicinally relevant compounds. Initial mechanistic studies are consistent with a rate-limiting oxidative addition that is facilitated by a magnesium Lewis-acid. The cross-coupling method has been extended to include aryl Grignard reagents for the asymmetric synthesis of triarylmethanes. The reaction proceeds in high enantiospecificity and employs an ether leaving group capable of chelating to magnesium ions. The method was applied to the asymmetric synthesis of an anti-breast-cancer agent.
Author: Lucas William Erickson
Publisher:
ISBN: 9780355307122
Category :
Languages : en
Pages : 321
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Book Description
In recent years, the Jarvo lab has developed the field of stereospecific nickel-catalyzed cross-coupling reactions of benzylic electrophiles. This chemistry allows for straightforward synthesis of asymmetric C--C bonds. The focus of this dissertation is on the study of the mechanism of these transformations, and the development of reductive cross-electrophile coupling reactions.First, the mechanism of the nickel-catalyzed Kumada cross-coupling reaction was studied via a 13C kinetic isotope effect experiment. This experiment indicated that oxidative addition of the nickel catalyst into the C--O sigma bond was the rate limiting step. Combining this data with a rate law allowed us to propose a catalytic cycle for this reaction. Additionally, the nickel-catalyzed deoxygenation of benzylic ethers was optimized for the formation of diaryl methanes. Deoxygenation performed best with a proton-rich Grignard reagent. We demonstrated that these Grignard reagents act as the hydride source for the reduction reaction.Next, an intramolecular nickel-catalyzed reductive cross-electrophile coupling reaction of benzylic ethers and alkyl chlorides was developed. This reaction proceeds with a variety of extended aromatic and heteroaromatic groups to produce cyclopropane rings in great yields and diastereoselectivity. This is the first example of a stereospecific reductive cross-electrophile coupling reaction, as well as the first to employ alkyl ethers and alkyl halides as the electrophiles.Finally, the work on nickel-catalyzed reductive cross-electrophile coupling reactions was expanded to synthesize vinylcyclopropanes from allylic ethers and alkyl halides. This reaction occurs with both alkyl fluorides and alkyl chlorides. To the best of our knowledge, this is the first reported cross-electrophile coupling reaction of an alkyl fluoride. Ring contraction proceeds with high stereospecificity, providing selective synthesis of either diastereomer of di- and tri-substituted cyclopropanes. The utility of this methodology is demonstrated by several synthetic applications including the synthesis of the natural product dictyopterene A. 2-Vinyl-4-fluorotetrahydrofurans also undergo stereospecific ring contractions, providing access to synthetically useful hydroxymethyl cyclopropanes.
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: Susan Lyn Zultanski
Publisher:
ISBN:
Category :
Languages : en
Pages : 176
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Book Description
Chapter 1 describes the development of two nickel-catalyzed Suzuki cross-coupling methodologies that employ alkyl halides as electrophiles. In Section 1.1, asymmetric [gamma]-alkylation relative to a carbonyl group is achieved via the stereoconvergent cross-coupling of racemic secondary [gamma]-chloroamides with primary alkylboranes. Section 1.2 describes the first Suzuki carbon-carbon bond-forming reaction using tertiary alkyl halides as electrophiles; specifically, unactivated tertiary alkyl bromides are cross-coupled with arylboranes. Chapter 2 describes the establishment of photoinduced asymmetric copper-mediated C-N Ullmann-type coupling processes between racemic secondary alkyl halides and N-heterocycles. Preliminary yields and enantioselectivities for a reaction between secondary benzylic halides and carbazoles, with the use of a monodentate chiral phosphine ligand, are presented. The methodology is then extended to secondary [alpha]-haloamides, including [alpha]-halolactams, which are found to afford very promising yields and enantioselectivities.
Author: Thomas C. Nugent
Publisher: John Wiley & Sons
ISBN: 9783527629558
Category : Science
Languages : en
Pages : 520
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Book Description
This first comprehensive presentation of this hot and important topic compiles the most up-to-date methods for chiral amine synthesis. The international list of authors reads like a "Who's Who" of the subject, providing a large array of highly practical information concentrated into the useful and essential methods. Following an introductory chapter devoted to helping readers quickly determine which strategies to choose for their investigation, this handbook and ready reference focuses on the examination of methods that are reliable and simultaneously efficient for the synthesis of structurally diverse aliphatic and aromatic chiral amines. Modern methods and applications found in (pharmaceutical) industry are also covered.
Author: Yasushi Nishihara
Publisher: Springer Science & Business Media
ISBN: 3642323685
Category : Science
Languages : en
Pages : 247
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Book Description
“Applied Cross-Coupling Reactions” provides students and teachers of advanced organic chemistry with an overview of the history, mechanisms and applications of cross-coupling reactions. Since the discovery of the transition-metal-catalyzed cross-coupling reactions in 1972, numerous synthetic uses and industrial applications have been developed. The mechanistic studies of the cross-coupling reactions have disclosed that three fundamental reactions: oxidative addition, transmetalation, and reductive elimination, are involved in a catalytic cycle. Cross-coupling reactions have allowed us to produce a variety of compounds for industrial purposes, such as natural products, pharmaceuticals, liquid crystals and conjugate polymers for use in electronic devices. Indeed, the Nobel Prize for Chemistry in 2010 was awarded for work on cross-coupling reactions. In this book, the recent trends in cross-coupling reactions are also introduced from the point of view of synthesis design and catalytic activities of transition-metal catalysts.
Author: Louis S. Hegedus
Publisher: University Science Books
ISBN: 9781891389047
Category : Science
Languages : en
Pages : 358
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Book Description
This second edition offers easy access to the field of organotransition metal chemistry. The book covers the basics of transition metal chemistry, giving a practical introduction to organotransition reaction mechanisms.
Author: Hélène Pellissier
Publisher: Royal Society of Chemistry
ISBN: 1847559247
Category : Science
Languages : en
Pages : 403
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Book Description
The goal of this book is to show the high potential of chiral sulfur-containing ligands to promote numerous asymmetric catalytic transformations. These ligands can now be recognised as real competitors to the more usual phosphorus- or nitrogen-containing ligands.
