Palladium Catalysed Cycloaddition Reactions PDF Download
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Author: Andrew James Teasdale
Publisher:
ISBN:
Category : Organotin compounds
Languages : en
Pages : 356
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Author: Andrew James Teasdale
Publisher:
ISBN:
Category : Organotin compounds
Languages : en
Pages : 356
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Author: Steven Clarkson
Publisher:
ISBN:
Category : Palladium catalysts
Languages : en
Pages : 366
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Author:
Publisher:
ISBN:
Category :
Languages : en
Pages :
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Author: W. Carruthers
Publisher: Elsevier
ISBN: 008091232X
Category : Science
Languages : en
Pages : 382
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Book Description
Demonstrates the wide scope of cycloaddition reactions, including the Diels-Alder reaction, the ene reaction, 1,3-dipolar cycloadditions and [2+2] cycloadditions in organic synthesis. The author, a leading exponent of the subject, illustrates the ways in which they can be employed in the synthesis of a wide range of carbocyclic and heterocyclic compounds, including a variety of natural products of various types. Special attention is given to intramolecular reactions, which often provide a rapid and efficient route to polycyclic compounds, and to the stereochemistry of the reactions, including recent and developing work on enantioselective synthesis.
Author: Shu Kobayashi
Publisher: John Wiley & Sons
ISBN: 9783527301591
Category : Science
Languages : en
Pages : 354
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Book Description
During the miners' strike in the 1980s, a worker is killed in the striking coalfields of Wales. Some months later, a government minister thought to be connected with the death is also shot. Lewis Redfern—once a radical but now a political analyst and journalist—pursues the sniper, a lonely hunt that leads him through an imbroglio of civil service leaks to a secret organization: a source of insurrection far more powerful than anyone could have suspected known as the Volunteers. In this fast-paced narrative of espionage and intrigue, Redfern, through his obsessive pursuit of justice, finally encounters the truth about himself as the novel discusses the conflict between moral choice and political loyalty.
Author: Angela Lynn Marquart
Publisher:
ISBN:
Category :
Languages : en
Pages : 128
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Author: Steven Mark Silverman
Publisher:
ISBN:
Category :
Languages : en
Pages :
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The development of new methods for chemical synthesis is motivated by the desire to add efficient chemo-, regio-, diastereo-, and enantioselective reactions to the repository of transformations available to researchers. In addition to reaction development, a primary goal of methodology research is to fundamentally understand chemical reactivity. This understanding provides the impetus for further discovery, inevitably allowing for the rapid synthesis of complex molecules as well as the development of industrially feasible processes. The research described herein discusses method development and seeks to place it within this context. Cycloaddition reactions have been widely used in organic synthesis since initial accounts of the Diels-Alder reaction were reported over 80 years ago. These reactions can proceed by either stepwise or concerted processes, can be thermally or photochemically initiated, metal catalyzed or non-metal catalyzed, but one unifying feature of this reaction class is the ability to quickly assemble a complex molecular architecture. A method for the synthesis of cyclopentane rings was disclosed by the Trost group in 1979 through the controlled generation of trimethylenemethane (TMM), a three-carbon dipole capable of participating in a palladium-catalyzed stepwise cycloaddition. Over the ensuing 20 years, this procedure was expanded to other five-membered rings, including pyrrolidines and tetrahydrofurans. It was generalized to include [4+3] and [6+3] cycloadditions in addition to the initial [3+2] reaction. However, only minimal advances were made in the establishment of a catalytic, asymmetric variant of the reaction, which would have enormous value in that chiral variants of the above molecules could be prepared. A protocol for the enantioselective TMM reaction was developed and is described herein. The synthesis of novel phosphoramidite ligands was critical in this effort, and the preparation and reactivity of these ligands is detailed. The evolution of the ligand design, commencing with acyclic amine-derived phosphoramidites and leading to cyclic azetidine and pyrrolidine structures is discussed. The initial conditions used to effect an asymmetric TMM reaction using 2-trimethylsilylmethyl allyl acetate were shown to be tolerant of a wide variety of alkene acceptors, providing the desired cyclopentanes with high levels of enantioselectivity. The donor scope was also explored and various substituted systems were tolerated, including one bearing a nitrile moiety and a one bearing a propiolate function. These were reactive with unsaturated acylpyrroles, giving the product cyclopentane rings bearing three stereocenters in high enantioselectivity and complete diastereoselectivity. The nitrile donor was reactive with methyleneoxindoles, providing products containing up to three adjacent stereocenters, two being all-carbon quaternary. Furthermore, ligand controlled diastereoselection was seen. The methodology was further applied to the synthesis of heterocycles. The parent donor successfully reacted with N-aryl and N-Boc imines. A nitrile donor was found to react with a series of N-Tosyl imines, giving the pyrrolidines in high yield. Multiple regioisomers were formed and reaction conditions were developed to favor each product. In the case of N-Tosyl ketimines, the desired cycloadducts containing tetrasubstituted centers were prepared with nearly complete enantio- and diastereoselectivity. The protecting group could be removed to afford a synthetically versatile compound with several handles for further elaboration. Conditions were also developed to perform an enantioselective TMM reaction with aldehydes, giving the desired tetrahydrofurans in moderate to good enantioselectivity. Finally, an asymmetric [4+3] cycloaddition utilizing ortho-quinone methides was successfully performed in an effort to prepare oxepanes. Taken collectively, these results demonstrate that the palladium-phosphoramidite catalyst system represents a versatile method for the rapid assembly of complex molecular architectures from simple starting materials via cycloaddition.
![Palladium and Gold-catalyzed Transannular [4+3] Cycloaddition Reactions PDF](https://books.google.com/books/content/images/frontcover/WHmmAQAACAAJ?fife=w80-h100)
Author: Derek T. Craft
Publisher:
ISBN:
Category : Catalysis
Languages : en
Pages : 185
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Unit I, Using allene RCM reactions, 12, 14 and 16 membered furan/allene macrocycles were synthesized. Selective epoxidation reactions and Platinum catalysis were unable to initiate a successful transannular [4+3] cycloaddition reaction from the 14 member macrocycle. However, a palladium catalyst system was then tested which produced the first reported example of a transannular [4+3] cycloaddition reaction in 37% yield. Gold catalysis showed a slight improvement on the product yield but competing rearrangement and [4+2] reactions were problematic. After changing the 3C component from an allene to a propargyl acetate, the reaction was optimized from 13 and 14 membered macrocycles using gold catalysis to generate [4+3] cycloadducts in high yield. The transannular [4+3] cycloaddition methodology was then applied to synthesizing the ABCD ring structure of Cortistatin A. Unit II, A short synthesis of S-(+)-Siphonodiol was completed utilizing a strategy which took advantage of the hidden symmetry of the molecule. Key steps in the synthesis were copper mediated alkyne coupling reactions. Unit III, Two new chiral N-Heterocyclic Carbene complexes were synthesized and the structures were confirmed using x-ray analysis. These complexes were found to be useful as catalysts and showed similar reactivity to Au(I)IPr in intramolecular cyclopropanation reactions from propargyl acetate/alkene substrates.
Author: Jonathan Robert Parquette
Publisher:
ISBN:
Category :
Languages : en
Pages : 754
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Author: Selvaratnam Suganthan
Publisher:
ISBN:
Category : Palladium catalysts
Languages : en
Pages : 394
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