Synthesis of 3,4-diazaphospholanes and Their Application to Asymmetric Catalysis PDF Download
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Author: Thomas P. Clark
Publisher:
ISBN:
Category :
Languages : en
Pages : 332
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Author: Thomas P. Clark
Publisher:
ISBN:
Category :
Languages : en
Pages : 332
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Author: Julia Wildt
Publisher:
ISBN:
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: Ryan C. Nelson
Publisher:
ISBN:
Category :
Languages : en
Pages : 276
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Author: Matt Adams
Publisher:
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Category :
Languages : en
Pages : 0
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This thesis presents a facile entry into diazaphospholene catalysis, harnessing pre- catalysts formed through the reaction of diazaphospholene-bromide compounds with neopentyl alcohol, to afford crystalline pre-catalysts. Their application in the hydroboration of imines and 1,4-reductions gives novel insight into their reactivity, as these heterocycles had yet to be employed in these catalyzed reactions. Mechanistic insights into the role of the catalyst, as well as potential decomposition pathways were explored. Next, enantioenriched diazaphospholene pre-catalysts were developed. These chiral pre-catalysts were applied in the asymmetric hydroboration of imines, to afford amines with enantiomeric ratios of up to 88:12. The monoamine oxidase inhibitor drug Rasagiline (employed in the treatment for Parkinson's disease) was synthesized through these methods affording high selectivity and is the first asymmetric synthesis of this drug. Finally, efforts towards the use of diazaphospheniums as Lewis acids in the splitting of dihydrogen, and hydrogenation of imines are described.
Author: Jianbo Wang
Publisher: World Scientific Publishing Europe Limited
ISBN: 9781786348890
Category : Science
Languages : en
Pages : 560
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Book Description
Diazo compounds are versatile substances with diverse transformations in organic synthesis and other fields. Studies of diazo compounds have been ongoing for a very long time but still attract significant attention within the organic chemistry community, with new papers related to diazo compounds appearing at a daily pace. Over the past twenty years, there have been over fifty reviews and accounts related to the reactions of diazo compounds, but most of them cover limited aspects of diazo compounds. In addition to organic synthesis, diazo compounds have found applications in interdisciplinary fields such as material sciences, chemical biology and also polymerization.In this comprehensive book, the authors cover the most recent advances in the fields related to diazo compounds, including the application of donor-acceptor carbenes, carbene-based cross-coupling reactions and polymerizations, as well as the breakthrough in catalytic asymmetric carbene O-H, S-H, and N-H bond insertions. They also cover the application of flow chemistry in diazo reactions. The authors aim to provide a contemporary and comprehensive review for investigators engaged in or with interest in diazo compounds to boost further developments in this fascinating field.
Author:
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ISBN:
Category : Medicine
Languages : en
Pages : 2160
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Book Description
Vols. for 1963- include as pt. 2 of the Jan. issue: Medical subject headings.
Author: Hong-feng Chen
Publisher:
ISBN:
Category :
Languages : en
Pages : 0
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Author: Aisling M. Lakes
Publisher:
ISBN:
Category : Asymmetric synthesis
Languages : en
Pages : 182
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Book Description
Author: Mariette M. Pereira
Publisher: Royal Society of Chemistry
ISBN: 1788010655
Category : Business & Economics
Languages : en
Pages : 300
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Book Description
Author: Vasyl Andrushko
Publisher: John Wiley & Sons
ISBN: 1118628330
Category : Science
Languages : en
Pages : 1836
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Book Description
Brings together the best tested and proven stereoselective synthetic methods Both the chemical and pharmaceutical industries are increasingly dependent on stereoselective synthetic methods and strategies for the generation of new chiral drugs and natural products that offer specific 3-D structures. With the publication of Stereoselective Synthesis of Drugs and Natural Products, researchers can turn to this comprehensive two-volume work to guide them through all the core methods for the synthesis of chiral drugs and natural products. Stereoselective Synthesis of Drugs and Natural Products features contributions from an international team of synthetic chemists and pharmaceutical and natural product researchers. These authors have reviewed the tremendous body of literature in the field in order to compile a set of reliable, tested, and proven methods alongside step-by-step guidance. This practical resource not only explores synthetic methodology, but also reaction mechanisms and applications in medicinal chemistry and drug discovery. The publication begins with an introductory chapter covering general principles and methodologies, nomenclature, and strategies of stereoselective synthesis. Next, it is divided into three parts: Part One: General Methods and Strategies Part Two: Stereoselective Synthesis by Bond Formation including C-C bond formation C-H bond formation C-O bond formation C-N bond formation Other C-heteroatom formation and other bond formation Part Three: Methods of Analysis and Chiral Separation References in every chapter serve as a gateway to the literature in the field. With this publication as their guide, chemists involved in the stereoselective synthesis of drugs and natural products now have a single, expertly edited source for all the methods they need.
