I. Palladium Catalyzed Reactions of Alkynes with Vinyl Bromides and Aryl Halides. II. Enantioselective Synthesis: Ruthenium Catalyzed Hydrogenation of B-keto Esters and Synthesis of (+)-brefeldin A PDF Download
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Author: Lee Jonathan Silverberg
Publisher:
ISBN:
Category :
Languages : en
Pages : 382
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Author: Lee Jonathan Silverberg
Publisher:
ISBN:
Category :
Languages : en
Pages : 382
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Author:
Publisher:
ISBN:
Category : Dissertations, Academic
Languages : en
Pages : 698
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Author: Fransisco Dean Toste
Publisher:
ISBN:
Category :
Languages : en
Pages : 1042
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Author: Jiro Tsuji
Publisher:
ISBN:
Category : Science
Languages : en
Pages : 596
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Book Description
Basic chemistry of organopalladium compounds; Classification of the reactions involving Pd(II) compounds and Pd(O) complexes.
Author: Yiyang Liu
Publisher:
ISBN:
Category : Electronic dissertations
Languages : en
Pages : 1012
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Book Description
Decarboxylation and decarbonylation are important reactions in synthetic organic chemistry, transforming readily available carboxylic acids and their derivatives into various products through loss of carbon dioxide or carbon monoxide. In the past few decades, palladium-catalyzed decarboxylative and decarbonylative reactions experienced tremendous growth due to the excellent catalytic activity of palladium. Development of new reactions in this category for fine and commodity chemical synthesis continues to draw attention from the chemistry community. The Stoltz laboratory has established a palladium-catalyzed enantioselective decarboxylative allylic alkylation of beta-keto esters for the synthesis of alpha-quaternary ketones since 2005. Recently, we extended this chemistry to lactams due to the ubiquity and importance of nitrogen-containing heterocycles. A wide variety of alpha-quaternary and tetrasubstituted alpha-tertiary lactams were obtained in excellent yields and exceptional enantioselectivities using our palladium-catalyzed decarboxylative allylic alkylation chemistry. Enantioenriched alpha-quaternary carbonyl compounds are versatile building blocks that can be further elaborated to intercept synthetic intermediates en route to many classical natural products. Thus our chemistry enables catalytic asymmetric formal synthesis of these complex molecules. In addition to fine chemicals, we became interested in commodity chemical synthesis using renewable feedstocks. In collaboration with the Grubbs group, we developed a palladium-catalyzed decarbonylative dehydration reaction that converts abundant and inexpensive fatty acids into value-added linear alpha olefins. The chemistry proceeds under relatively mild conditions, requires very low catalyst loading, tolerates a variety of functional groups, and is easily performed on a large scale. An additional advantage of this chemistry is that it provides access to expensive odd-numbered alpha olefins. Finally, combining features of both projects, we applied a small-scale decarbonylative dehydration reaction to the synthesis of alpha-vinyl carbonyl compounds. Direct alpha-vinylation is challenging, and asymmetric vinylations are rare. Taking advantage of our decarbonylative dehydration chemistry, we were able to transform enantioenriched delta-oxocarboxylic acids into quaternary alpha-vinyl carbonyl compounds in good yields with complete retention of stereochemistry. Our explorations culminated in the catalytic enantioselective total synthesis of (-)-aspewentin B, a terpenoid natural product featuring a quaternary alpha-vinyl ketone. Both decarboxylative and decarbonylative chemistries found application in the late stage of the total synthesis.
Author: Sharon Husak
Publisher:
ISBN: 9780494274385
Category :
Languages : en
Pages : 142
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The effect of changing the allylic group in a palladium-catalyzed direct cross-coupling between aryl halides and allylic moieties was examined. beta-Heteroatom elimination was found to preferentially occur over beta-hydride elimination for substrates possessing an allylic moiety containing a good leaving group. Extension of the reaction conditions to the intramolecular coupling of aryl iodides and allylic alcohols allows for the rapid synthesis of a variety of carbo- and herterocycles containing aldehyde functionalities in good to excellent yields. Optimization of the palladium-catalyzed cross-coupling reaction between a vinyl halide and allyl carbonate allowed for the efficient synthesis of six-membered nitrogen-containing cycles. The nature of the leaving group strongly influences the yield of the coupling reaction. Application of the optimized conditions to the intramolecular cyclization of a vinyl iodide and allylic alcohol indicates the utility of this methodology in the formation of carbonyl-containing heterocycles.
Author: Karen Marie Miller
Publisher:
ISBN:
Category :
Languages : en
Pages : 374
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Book Description
Catalytic addition reactions to alkynes are among the most useful and efficient methods for preparing diverse types of substituted olefins. Controlling both regioselectivity and (EIZ)- selectivity in such transformations presents a significant challenge. In reactions that also involve the creation of a new stereocenter, the development of enantioselective processes is highly desirable. Several novel, nickel-catalyzed carbon-carbon bond-forming reactions of alkynes that display excellent regioselectivity and (E/Z)-selectivity are described. These reactions afford synthetically useful allylic and homoallylic alcohols, often with high enantioselectivity. A highly enantioselective method for the nickel-catalyzed reductive coupling of alkynes and aldehydes has been realized using the commercially available (+)- neomenthyldiphenylphosphine as a chiral ligand. Allylic alcohols are afforded with complete (E/Z)-selectivity, generally>95:5 regioselectivity, and in up to 96% ee. In conjuction with ozonolysis, this process is complementary to existing methods of enantioselective [alpha]-hydroxy ketone synthesis. In alkene-directed, nickel-catalyzed reductive couplings of 1,3-enynes with aldehydes and epoxides, the conjugated alkene dramatically enhances reactivity and uniformly directs regioselectivity, independent of the nature of the other alkyne substituent (aryl, alkyl (1°, 2°, 3°)) or the degree of alkene substitution (mono-, di-, tri-, and tetrasubstituted). The highly substituted 1,3-diene products are useful in organic synthesis and, in conjunction with a Rh-catalyzed, siteselective hydrogenation, afford allylic and homoallylic alcohols that previously could not be prepared in high regioselectivity (or at all) with related Ni-catalyzed alkyne coupling reactions. Enantiomerically enriched terminal epoxides can be employed to afford enantiomerically enriched homoallylic alcohols. P-chiral, monodentate ferrocenyl phosphine ligands are efficient promoters of catalytic, asymmetric reductive coupling reactions of 1,3-enynes with aromatic aldehydes and with ketones. The latter represents the first catalytic intermolecular reductive coupling of alkynes and ketones, asymmetric or otherwise, to be reported. Both of these methods afford chiral 1,3-dienes in excellent regioselectivity and modest enantioselectivity. Nickel-catalyzed reductive couplings of 1,6-enynes and aldehydes also display very high (>95 : 5) regioselectivity. Use of a monodentate phosphine as an additive leads to formation of the opposite regioisomer in equal and opposite selectivity (5:>95). These results provide strong evidence for an interaction between the remote alkene and the metal center during the regioselectivity-determining step.
Author: Elizabeth Claire Swift
Publisher:
ISBN: 9781303328121
Category :
Languages : en
Pages : 337
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Transition-metal catalysis has enabled the development of an unprecedented number of mild and selective C-C bond-forming reactions. We sought to access the reactivity of palladium and nickel catalysts for two types of transformations: conjugate allylations and sp3-sp3 cross-coupling reactions. Conjugate allylation of malononitriles was evaluated with N-heterocyclic carbene-ligated palladium complexes. The allylation was found to yield a variety of mono-allylated products. These results are in contrast to the bis-allylation of malononitriles using other palladium-based catalysts. Additionally, conjugate addition of [alpha], [beta]-unsaturated N-acylpyrroles was found to be accelerated in the presence of sulfoxide substitution on the pyrrole ring. These substrates are lead compounds for the development of an enantioselective allylation reaction. Transition metal-catalyzed cross-coupling reactions have become standard practice in organic synthesis. Recent advances in alkyl-alkyl couplings have been transformative in the way organic chemists approach the construction of target molecules. This dissertation focuses on the development of stereospecific sp3-sp3 cross-coupling reactions. We discovered that in the presence of nickel catalysts, secondary benzylic ethers were found to undergo stereospecific substitution reactions with Grignard reagents. Reactions proceeded with inversion of configuration and high stereochemical fidelity. This reaction allows for facile enantioselective synthesis of biologically active diarylethanes from readily available optically enriched carbinols. Subsequently, this reaction was expanded to dialkylzinc reagents and the first stereospecific Negishi cross-coupling reaction of secondary benzylic esters was developed. A series of traceless directing groups were evaluated for their ability to promote cross-coupling with dimethylzinc. Esters with a chelating thioether derived from commercially-available 2-(methylthio)acetic acid were found to be the most effective. The products were formed in high yield and with excellent stereospecificity. A variety of functional groups were tolerated in the reaction including alkenes, alkynes, esters, amines, imides, and O-, S-, and N-heterocycles. The utility of this transformation was highlighted in the enantioselective synthesis of a retinoic acid receptor (RAR) agonist.
Author: Ei-ichi Negishi
Publisher: Wiley-Interscience
ISBN: 0471461555
Category : Science
Languages : en
Pages : 3424
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Book Description
Organized to provide maximum utility to the bench synthetic chemist. The editor is well-known for his work in exploring, developing, and applying organopalladium chemistry. Contributors include over 24 world authorities in the field.
Author: Seble-Hiwot Teshome Wagaw
Publisher:
ISBN:
Category :
Languages : en
Pages : 280
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