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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.
The last 15 years have witnessed significant developments in the
efficiency and scope of the application of DKR. These now offer a
serious alternative to conventional methods for asymmetric
synthesis. Indeed, impressive examples using new enzymes and major
progress in the DKR of racemates have taken place over the past few
years. The powerful combination of enzymes and metals has also been
the subject of spectacular development. In addition, a new type of
DKR, involving organocatalysts, has recently appeared. Although
asymmetric catalysis has undergone development during the last two
decades, the most common industrial process used to obtain
enantiomerically pure compounds is still via resolution of racemic
mixtures. This is despite the major disadvantage that only a
maximum of 50% product yield can be obtained. It is not surprising
that DKR, which solves the problem of the limitation in yield, has
attracted an increasing amount of interest from both the industrial
and the academic perspective. This book provides an up-date on the
principle methods employed to obtain dynamic kinetic resolution
(DKR) by either enzymatic or non-enzymatic methods. It also
illustrates the diversity of useful chiral products that can be
obtained through this powerful concept. Divided into three
sections, the book deals successively with non-enzymatic methods,
enzymatic methods, and the use of transition metals and enzymes in
tandem.
The aim of this book is to cover the very recent developments in
asymmetric organocatalysis, focussing on those published since the
beginning of 2008. The last decade has witnessed an explosive
growth in the field of asymmetric organocatalysis with an
impressive amount of new catalysts, novel methodologies, and
applications in numerous reaction types, such as nucleophilic
substitutions, addition reactions, as well as cycloadditions,
oxidations, reductions, kinetic resolutions, and miscellaneous
reactions. This very diverse and intensely developing field is too
wide to cover in a single review. The timeliness of the book
together with the expected impact is excellent, since nowadays
asymmetric organocatalysis is arguably the most intensively
developed field in organic chemistry. The book is designed to meet
the demands of a postgraduate textbook,containing case studies and
Q&A sections, as well as a practical book filled with facts and
data useful as a working tool for the practitioner. The book is
divided into ten sections, dealing successively with nucleophilic
additions to electron-deficient C=C double bonds, nucleophilic
additions to C=O double bonds, nucleophilic additions to C=N double
bonds, nucleophilic additions to unsaturated nitrogen, nucleophilic
substitutions at aliphatic carbon, cycloaddition reactions,
oxidations, reductions, kinetic resolutions and desymmetrisations,
and miscellaneous reactions.
The goal of this book is to show the high potential of chiral
sulfur-containing ligands to promote numerous asymmetric catalytic
transformations. The important number of reports appeared in the
literature over the last 35 years often highlighted spectacular
results in terms of efficiency and enantioselectivity, allowing
access to many biologically important molecules, which clearly
demonstrates that these ligands can now be recognised as real
competitors to the more usual phosphorus- or nitrogen-containing
ligands. A key point of reference for post-graduate students,
researchers and academics.
Indole derivatives are the most common heterocycle compounds
present in nature, for this reason, they have been referred to as
'privileged structures'. In fact, many approved drugs - and natural
products - belong to this family. Among indole derivatives,
oxindoles have a structural complexity, which have stimulated
generations of synthetic chemists to design strategies for
assembling these structures, and their enantioselective synthesis
is still growing.This book proposes to describe the known
enantioselective syntheses of oxindole derivatives. It is divided
in six chapters each referring to a specific class of asymmetric
oxindole derivatives. After the introduction, Chapter 2 describes
all-carbon spirooxindoles; Chapter 3, open chain
3,3-dialkyloxindoles; Chapter 4, 3-substituted-3-aminooxindoles;
Chapter 5, 3-substituted-3-hydroxyoxindoles; Chapter 6,
3-hetero-3-substituted oxindoles. It will be a useful tool for
synthetic chemists, who assemble total synthesis of natural
products, as well as for drug discovery chemists either in academic
or in industry R&S laboratories.
In a classical kinetic resolution, two enantiomers of a racemate
are transformed into chiral products at different rates with a
maximum theoretical yield of 50%. However, the need to reduce costs
and waste in synthesis have led to efforts to develop novel
resolution procedures proceeding beyond this 50% limited yield.
This has led to the evolution of classical kinetic resolution into
dynamic kinetic resolution (DKR), allowing a quantitative yield of
one of the enantiomers. DKR combines the resolution step of kinetic
resolution with an in-situ racemization of the chirally-labile
substrate. It is only in the last two decades that chiral green
organocatalysts have been demonstrated to be capable of promoting
DKRs considerably expanding the synthetic scope of the powerful
concept of DKR. Collecting all the developments in the field of
DKR, this book shows that a wide variety of organocatalysts allow
excellent levels of stereocontrol and yields in many types of
transformations. It is a great resource for academics and
industrialists interested in green enantioselective catalytic
reactions.
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.
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