Catalytic Diastereo- and Enantioselective Formation of All-carbon Quaternary Centers: Ir-catalyzed Tert-(hydroxy)prenylation of Alcohols and Its Application to Modular Syntheses of Terpenoids PDF Download
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Author: Jiajie Feng
Publisher:
ISBN:
Category :
Languages : en
Pages : 688
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Book Description
All-carbon quaternary stereocenters are ubiquitous in bioactive natural products as well as pharmaceutical molecules. However, stereoselective access of these structural motifs is still a challenge in synthetic chemistry. Therefore, a general method that can construct quaternary carbon centers diastereo- and enantioselectively is in high demand. Redox-triggered stereoselective C-C bond forming reactions via metal-catalyzed transfer hydrogenation are able to avoid usage of sensitive preformed organometallic reagents and formation of stoichiometric metal waste. Efforts have been focused on the development of efficient methods for diastereo- and enantioselective generation of quaternary centers via iridium-catalyzed tert-(hydroxy)prenylation of alcohols and aldehydes. Applying this methodology to modular syntheses of terpenoid natural products oridamycin A, triptoquinones B and C, isoiresin and andrographolide in the most concise routes is described.
Author: Jiajie Feng
Publisher:
ISBN:
Category :
Languages : en
Pages : 688
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Book Description
All-carbon quaternary stereocenters are ubiquitous in bioactive natural products as well as pharmaceutical molecules. However, stereoselective access of these structural motifs is still a challenge in synthetic chemistry. Therefore, a general method that can construct quaternary carbon centers diastereo- and enantioselectively is in high demand. Redox-triggered stereoselective C-C bond forming reactions via metal-catalyzed transfer hydrogenation are able to avoid usage of sensitive preformed organometallic reagents and formation of stoichiometric metal waste. Efforts have been focused on the development of efficient methods for diastereo- and enantioselective generation of quaternary centers via iridium-catalyzed tert-(hydroxy)prenylation of alcohols and aldehydes. Applying this methodology to modular syntheses of terpenoid natural products oridamycin A, triptoquinones B and C, isoiresin and andrographolide in the most concise routes is described.
Author: Corey Michael Reeves
Publisher:
ISBN:
Category :
Languages : en
Pages : 0
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Book Description
Notwithstanding advances in modern chemical methods, the selective installation of sterically encumbered carbon stereocenters, in particular all-carbon quaternary centers, remains an unsolved problem in organic chemistry. The prevalence of all-carbon quaternary centers in biologically active natural products and pharmaceutical compounds provides a strong impetus to address current limitations in the state of the art of their generation. This thesis presents four related projects, all of which share in the goal of constructing highly-congested carbon centers in a stereoselective manner, and in the use of transition-metal catalyzed alkylation as a means to address that goal. The first research described is an extension of allylic alkylation methodology previously developed in the Stoltz group to small, strained rings. This research constitutes the first transition metal-catalyzed enantioselective alpha-alkylation of cyclobutanones. Under Pd-catalysis, this chemistry affords all - carbon alpha-quaternary cyclobutanones in good to excellent yields and enantioselectivities. Next is described our development of a (trimethylsilyl)ethyl beta-ketoester class of enolate precursors, and their application in palladium-catalyzed asymmetric allylic alkylation to yield a variety of alpha-quaternary ketones and lactams. Independent coupling partner synthesis engenders enhanced allyl substrate scope relative to allyl beta-ketoester substrates; highly functionalized alpha-quaternary ketones generated by the union of our fluoride-triggered beta-ketoesters and sensitive allylic alkylation coupling partners serve to demonstrate the utility of this method for complex fragment coupling. Lastly, our development of an Ir-catalyzed asymmetric allylic alkylation of cyclic beta-ketoesters to afford highly congested, vicinal stereocenters comprised of tertiary and all-carbon quaternary centers with outstanding regio-, diastereo-, and enantiocontrol is detailed. Implementation of a subsequent Pd-catalyzed alkylation affords dialkylated products with pinpoint stereochemical control of both chiral centers. The chemistry is then extended to include acyclic bega-ketoesters and similar levels of selective and functional group tolerance are observed. Critical to the successful development of this method was the employment of iridium catalysis in concert with N-aryl-phosphoramidite ligands.
Author: Angela Marinetti
Publisher: World Scientific
ISBN: 9811248443
Category : Science
Languages : en
Pages : 501
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Book Description
This book illustrates the broad field of enantioselective catalysis by highlighting a few topics, out of myriads, with the double aim to typify selected synthetic achievements and future challenges. Eleven research groups have highlighted topics of interest in either organo- or organometallic catalysis, related to their own expertise. For mature fields, these short chapters, far from being exhaustive, show updated overviews including major recent advances and disclose a few prospects. Other chapters focus on upcoming topics in enantioselective catalysis, i.e. on classes of reactions or families of catalysts that are expected to provide appealing synthetic tools when suitably mastered. For all these areas, recent studies demonstrate highly promising perspectives.
Author: Hélène Pellissier
Publisher: Royal Society of Chemistry
ISBN: 1788015150
Category : Science
Languages : en
Pages : 375
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Book Description
With a foreword from leading organic chemist Professor Paul Wender, this book collects the major developments reported in the past thirty years in the field of enantioselective reactions promoted by chiral cobalt catalysts, illustrating the power of these green catalysts to provide all types of organic reactions from the basic to completely novel methodologies. The search for new methodologies to prepare optically pure products is one of the most active areas of research in organic synthesis. Of the methods available for preparing chiral compounds, catalytic asymmetric synthesis has attracted the most attention. In particular, asymmetric transition-metal catalysis is a powerful tool for performing reactions in a highly enantioselective fashion. Efforts to develop new asymmetric transformations have previously focused on the use of rare metals such as titanium, palladium, iridium and gold. However, the ever-growing need for environmentally friendly catalytic processes has prompted chemists to focus on the more abundant and less toxic first-row transition metals, such as cobalt, to develop new catalytic systems. The ability of cobalt catalysts to adopt unexpected reaction pathways has led to an impressive number of enantioselective cobalt-promoted transformations being developed over the past three decades. These have included the synthesis of many different types of products, often under relatively mild conditions and with remarkable enantioselectivities. This book is a useful reference resource for chemists, both academic and industrial, working in organic synthesis and interested in greener or more economical catalytic alternatives.
Author: Peter I. Dalko
Publisher: John Wiley & Sons
ISBN: 3527610952
Category : Science
Languages : en
Pages : 559
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Book Description
In this reference leaders at the forefront of research provide an insight into one of the hottest topics in organic synthesis, focusing on the most important enantioselective reactions. Clearly structured, each entry begins with a concise introduction, including a mechanistic discussion of the reaction, followed by preparative guidelines for newcomers, such as carefully selected working procedures with critical notes for bench chemists, rules of thumb and tips and tricks.
Author: Jose L Vicario
Publisher: Royal Society of Chemistry
ISBN: 1849732183
Category : Science
Languages : en
Pages : 365
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Book Description
This book, unique in its field, is a comprehensive description of all the methodologies reported for carrying out conjugate addition reactions in a stereoselective way, using small chiral organic molecules as catalysts (organocatalysts). In the last 3-4 years, this has been a rapidly growing field in organic chemistry, and many papers have appeared reporting excellent protocols for carrying out these highly efficient transformations that compete well with other classical approaches using transition metal catalysts. A particularly attractive feature of this transformation relies upon the fact that the conjugate addition (Michael and Hetero-Michael reactions) is an extraordinarily effective means to initiate cascade processes which result in the formation of complex molecules from very small and simple starting blocks. The book, written by noted experts, covers all recent advances in this hot topic, and provides a good state-of-the-art review for organic chemists working in this field and all those who wish to start projects in this area.
Author: Radovan Sebesta
Publisher: Royal Society of Chemistry
ISBN: 1849733422
Category : Science
Languages : en
Pages : 301
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Book Description
Immobilization of chiral catalysts is an important tool for improving overall efficiency of catalytic processes. However, heterogeneous catalysts often suffer from decreased activities and supported but still homogeneous catalysts can help overcome this issue. This book covers the most important concepts of homogeneous supported catalysis with an emphasis on enantioselective processes. It describes the state-of-the-art and latest developments in each area whilst critically evaluating the strengths and weaknesses of this important method. The book encompasses ionically-tagged catalysts, supported organocatalysts, supported ionic liquid phases, catalysis using soluble polymers, catalytic dendrimers, fluorous catalysts, water soluble catalysts and non-covalent immobilization methods. Potential developments and ideas for the future are also highlighted. There is a growing demand for effective and recyclable catalysts so this book, covering all the important methods in the field of supported homogeneous catalysis, will appeal to many researchers in academia and industry.
Author: Helene Pellissier
Publisher: Royal Society of Chemistry
ISBN: 1782621350
Category : Science
Languages : en
Pages : 255
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Book Description
Chiral molecules are needed for the production of many pharmaceuticals and materials, and catalytic asymmetric synthesis provides a method for the preparation of such chiral products. For the synthesis of complex molecules, such as natural products and biologically active compounds, more than one catalytic reaction may be necessary and tandem catalysis refers to the combination of catalytic reactions into one synthesis. By combing catalysts it enables a more efficient, economical and selective one pot approach for complex molecule synthesis which could not be achieved through single specific catalytic systems. The challenge is finding the right catalyst which is compatible with other catalysts but also tolerates reagents, solvent and intermediates generated during the course of the reaction. Enantioselective Multicatalysed Tandem Reactions provides an overview of recent developments in the area. The first part of the book covers asymmetric tandem reactions catalysed by multiple catalysts from the same discipline (organocatalysts, two metal and multienzyme-catalysed reactions). The second part looks at tandem reactions catalysed by multiple catalysts from different disciplines including reactions catalysed by a combination of metals and organocatalysts, reactions catalysed by a combination of metals and enzymes, and finally reactions catalysed by a combination of organocatalysts and enzymes. The book will appeal to researchers and professionals in academic and industrial laboratories interested in catalysis, biocatalysis and organic synthesis of chiral compounds.
Author: Helene Pellissier
Publisher: World Scientific
ISBN: 1783268964
Category : Science
Languages : en
Pages : 278
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Book Description
Chiral titanium complexes are low-cost, low-toxicity and high-efficiency catalysts. Impressive progress on enantioselective titanium-catalysed transformations has been achieved in the past seven years, with exciting new discoveries ranging from basic reactions to novel methodologies. Despite this, the field has not been substantially reviewed since 2008.This book contains up to date research and covers all types of enantioselective transformations using chiral titanium catalysts. It illustrates the economic, health, and environmental benefits of chiral titanium catalysts, showing the types of highly enantioselective reactions that they are able to induce are unlimited.Work presented here is aimed at researchers in organic and catalytic chemistry, and has been carefully curated to encourage future research possibilities.
Author: Tse-Lok Ho
Publisher: Wiley-Interscience
ISBN:
Category : Science
Languages : en
Pages : 340
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Book Description
In recent years the intense activities of enantioselective synthesis have been reflected in the burgeoning and ingenious applications of such natural substances as carbohydrates, -amino acids and terpenes. A comprehensive summary of terpene-based synthesis is offered, focusing on synthetic efforts using transformed chiral synthons. The author provides analysis of synthetic strategies and discusses the intricacies of reaction courses. Along with the number and variety of natural products derived from chiral terpenes, numerous flow-charts aid in clearly delineating synthetic pathways.
