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| Author | : Arun A. (Arun Anil) Narine |
| Publisher | : Library and Archives Canada = Bibliothèque et Archives Canada |
| Total Pages | : 590 |
| Release | : 2004 |
| Genre | : Asymmetric synthesis |
| ISBN | : |
| Author | : Arun A. Narine |
| Publisher | : |
| Total Pages | : 0 |
| Release | : 2004 |
| Genre | : Asymmetric synthesis |
| ISBN | : |
Task definition theoretically is one of the main components of self-regulated learning because one's representation of the task directs cognitive activities such as setting goals, creating plans, and enacting those plans to create task products. To date, little research has examined students' representations of tasks or how those representations change over time. In this dissertation I characterize students' initial representations of tasks and explore factors influencing how they refine these representations over time. Fifty-eight undergraduate students taking an undergraduate instructional psychology course participated in a semester-long examination of how students constructed and refined their task understanding. The data source was a studying portfolio consisting of detailed descriptions about and reflections on strategic processes they used to complete two main writing assignments in the course: a think paper and a design project. Analyses of these data suggest students' representations of tasks varied across two dimensions: breadth and depth. In terms of breadth, students selected information from the design project description of different grain sizes. Students with greater depth not only searched and selected information from the task, but they actively assembled elements of the task and monitored how those components fit with one another. Most students set goals and created plans; however, not all goals or plans were framed in light of criteria that would theoretically foster self-regulated learning. To revise task understanding, students metacognitively monitored their processes and outcomes of learning activities, which updated information about task, cognitive, and motivational conditions. This additional information afforded students opportunity to reassess the discrepancy between the initial state and the goal state to determine next steps to reach task goals. Although students may have recognized the need to change their approaches, they often failed to engage in effective metacognitive control to adapt approaches to learning. I interpret this to indicate that control processes require not only the skill for enacting these processes but also the motivational catalyst to sustain these efforts when competing factors are present. Future research should strive to create new measures for task understanding, and to track how students' perceptions and representations of tasks influence self-regulated learning and achievement.
| Author | : Michael P. A. Lyle |
| Publisher | : |
| Total Pages | : 0 |
| Release | : 2005 |
| Genre | : Asymmetric synthesis |
| ISBN | : |
The work described in this thesis concerns the design, synthesis and evaluation of new chiral nonracemic ligands and catalysts for use in asymmetric reactions. A series of chiral nonracemic chloroacetals were prepared from 2-chloro-4- methyl-6,7-dihydro-5H-[l]pyrindine-7-one and a variety of C2-symmetric and chiral nonracemic 1,2-ethanediols (R = Me, i-Pr and Ph). These chloroacetals were further elaborated, in a modular fashion, to provide a series of chiral ligands and catalysts. A new class of C2-symmetric 2,2'-bipyridyl ligands were prepared in one step fiom the chloroacetals via a nickel(0)-mediated homo-coupling reaction. These ligands were then evaluated as chiral directors in copper@)-catalyzed asymmetric cyclopropanation reactions of styrene and diazoesters (up to 44% ee). A chiral pyridine N-oxide and a C2-symmetric 2,2'-bipyridyl N, N'-dioxide were also prepared by direct oxidation of the corresponding pyridine and the 2,2'-bipyridine, respectively. These chiral N-oxides were evaluated as chiral catalysts in desymmeterization reactions of cis-stilbene oxide (up to 20% ee). A series of pyridylphosphine ligands (P, N-ligands) were subsequently prepared in two steps from the chloroacetals via a Suzuki coupling reaction with orthofluorophenylboronic and on subsequent displacement of the fluoride with the potassium anion of diphenylphosphine. These ligands were then evaluated in palladium-catalyzed asymmetric allylic substitution reactions of racemic 3-acetoxy-l,3-diphenyl-1-propene with dimethyl malonate. Optimization of the reaction conditions resulted in the formation of the alkylated product in excellent yield (91%) and in high enantiomeric excess (90%). A related chiral nonracemic and C2-symmetric 2,2'-bipyridyl ligand was prepared from 2-chloro-4-methyl-5H-[llpyrindine. This pyrindine was prepared from a common intermediate that was used in the synthesis of the first generation of ligands. The chirality of this second generation ligand was installed by a Sharpless asymmetric dihydroxylation reaction (90% ee). The subsequently elaborated 2,2'-bipyridyl ligand (enriched to>99% ee) was then evaluated in copper(1)-catalyzed asymmetric cyclopropanation reactions of alkenes and diazoesters. In the case of the reaction of para-fluorostyrene and tert-butyl diazoacetate, the corresponding cyclopropane was formed in good diastereoselectivity (92:8) and in excellent enantioselectivity (99% ee). This ligand was also evaluated in copper(I1)-catalyzed asymmetric Friedel-Crafts alkylation reactions of various substituted indoles (up to 90% ee) and in copper(1)- catalyzed asymmetric allylic oxidation reactions of cyclic alkenes with tert-butyl peroxybenzoate (up to 9 1 % ee).
| Author | : Montserrat Diéguez |
| Publisher | : CRC Press |
| Total Pages | : 298 |
| Release | : 2021-05-13 |
| Genre | : Science |
| ISBN | : 1000379000 |
Many new drugs on the market are chiral compounds, that is, they can exist in two non-superimposable mirror-image forms. Asymmetric catalysis encompasses a large variety of processes for obtaining such compounds. The performance of the catalyst in those processes largely depends on the ligand that makes up the catalyst. This book describes the most relevant ligand libraries for some key processes, including an overview of the state of art and the key mechanistic aspects that favor a high catalytic performance. Key Features: The book presents historical content from the time of discovery for each family of ligands. Provides a description of the synthetic route and the ligand library's application in various catalytic asymmetric reactions Suitable as supplementary reading for courses targeting the design, synthesis and application of chiral catalysts, asymmetric catalysis and sustainable production Edited by a distinguished scientist in the field, the book has a diverse audience including research groups in homogeneous catalysis, particularly asymmetric transformations
| Author | : J. Seyden-Penne |
| Publisher | : Wiley-Interscience |
| Total Pages | : 744 |
| Release | : 1995-10-23 |
| Genre | : Science |
| ISBN | : |
Table of Contents Preface Abbreviations Introduction 1 1 Enantiomerically Pure Chiral Auxiliaries 43 2 Chiral Reagents 87 3 Chiral Catalysis and Catalysts Bearing Chiral Ligands 117 4 Asymmetric Deprotonations and Protonations 143 5 Alkylations and Related Reactions 157 6 Additions to C=O and C=N Double Bonds 209 7 Additions to Carbon-Carbon Double Bonds 367 8 Additions to Double Bonds Bearing Heteroatoms. Oxidations of Sulfides and Selenides 503 9 Cycloadditions 513 10 Sigmatropic Rearrangements 593 11 Transition Metal Catalyzed Reactions 619 References 637 Index 707.
| Author | : Shinichi Itsuno |
| Publisher | : John Wiley & Sons |
| Total Pages | : 674 |
| Release | : 2011-06-28 |
| Genre | : Technology & Engineering |
| ISBN | : 1118063953 |
This book reviews chiral polymer synthesis and its application to asymmetric catalysis. It features the design and use of polymer-immobilized catalysts and methods for their design and synthesis. Chapters cover peptide-catalyzed and enantioselective synthesis, optically-active polymers, and continuous flow processes. It collects recent advances in an important field of polymer and organic chemistry, with leading researchers explaining applications in academic and industry R & D.
| Author | : Qi-Lin Zhou |
| Publisher | : John Wiley & Sons |
| Total Pages | : 670 |
| Release | : 2011-02-10 |
| Genre | : Technology & Engineering |
| ISBN | : 3527635211 |
Catalytic asymmetric synthesis has been one of the most active research areas in chemistry (Nobel Prize in 2001). The development of efficient chiral catalysts plays a crucial role in asymmetric catalysis. Although many chiral ligands/catalysts have been developed in the past decades, the most efficient catalysts are derived from a few core structures, called "privileged chiral catalysts". This ultimate "must have" and long awaited reference for every chemist working in the field of asymmetric catalysis starts with the core structure of the catalysts, explaining why a certain ligand or catalyst is so successful. It describes in detail the history, the basic structural characteristics, and the applications of these "privileged catalysts". This novel presentation provides readers with a much deeper insight into the topic and makes it a must-have for organic chemists, catalytic chemists, chemists working with/on organometallics, chemists in industry, and libraries. From the contents: * BINAP * Bisphosphacycles - From DuPhos and BPE to a Diverse Set of Broadly Applied Ligands * Josiphos Ligands: From Discovery to Technical Applications * Chiral Spiro Ligands * Chiral Bisoxazoline Ligands * PHOX Ligands * Chiral Salen Complexes * BINOL * TADDOLate Ligands * Cinchona Alkaloids * Proline Derivatives
| Author | : Bin Tan |
| Publisher | : John Wiley & Sons |
| Total Pages | : 338 |
| Release | : 2021-08-16 |
| Genre | : Science |
| ISBN | : 3527825185 |
Axially Chiral Compounds Explore this comprehensive and current volume summarizing the characteristics, synthesis, and applications of axial chirality Appearing widely in natural products, biologically active molecules, asymmetric chemistry, and material science, axially chiral motifs constitute the core backbones of the majority of chiral ligands and organocatalysts in asymmetric catalysis. In a new work of particular relevance to synthetic chemists, Axially Chiral Compounds: Asymmetric Synthesis and Applications delivers a clearly structured and authoritative volume covering the classification, characteristics, synthesis, and applications of axial chirality. A must read for every synthetic chemist practicing today, the book follows the development history, research status, and applications of axial chirality. An introductory chapter familiarizes the reader with foundational material before the distinguished authors describe the different classes and the synthesis of axial chiral compounds used in asymmetric synthesis. The book concludes with a focus on the applications of chiral ligands, chiral catalysts, and materials. Readers will also benefit from the inclusion of: A thorough introduction to asymmetric synthesis, including biaryls atropisomers, heterobiaryls atropisomers, and non-biaryls atropisomers Explorations of chiral allene, spiro skeletons, and natural products Practical discussions of asymmetric transformation, chiral ligands, and chiral catalysts An examination of miscellaneous applications of axially chiral compounds Perfect for organic chemists, chemists working with or on organometallics, catalytic chemists, and materials scientists, Axially Chiral Compounds: Asymmetric Synthesis and Applications will also earn a place in the libraries of natural products chemists who seek a one-stop reference for compounds exhibiting axial chirality.
| Author | : Li-Xin Dai |
| Publisher | : John Wiley & Sons |
| Total Pages | : 433 |
| Release | : 2010-02-01 |
| Genre | : Science |
| ISBN | : 3527322809 |
This book meets the long-felt need for a reference on ferrocenes with the focus on catalysis. It provides a thorough overview of the synthesis and characterization of different types of chiral ferrocene ligands, their application to various catalytic asymmetric reactions, and versatile chiral materials as well as drug intermediates synthesized from them. Written by the "who's who" of ferrocene catalysis, this is a guide to the design of new ferrocene ligands and synthesis of chiral synthetic intermediates, and will thus be useful for organic, catalytic and synthetic chemists working in academia, industrial research or process development.
| Author | : Hélène Pellissier |
| Publisher | : Royal Society of Chemistry |
| Total Pages | : 403 |
| Release | : 2009 |
| Genre | : Science |
| ISBN | : 1847559247 |
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.
