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Stimulating Concepts in Chemistry
Editors: Fritz Vögtle, J. Fräser Stoddart, Masakatsu Shibasaki
©WILEY-VCH Weinheim • New York • Chichester Brisbane • Singapore • Toronto
Table of Contents
New types of Lewis acids as water-stable catalysts have been developed. These Lewis acids activate Substrates such as aldehydes efficiently in aqueous media. Furthermore, surfactant-aided Lewis acid catalysis has also been used for reac-tions in water without using any organic solvents.
H2q
FAH
OH2
,-Mn+---OH2
I
OH,
S. Kobayashi,
K. Manabe
Lewis Acid Catalysis
in Aqueous Media
Supercritical fluid (SCF) with the beneficial effects of both liquid- and gas-phase chemistry is an emerging reaction medium for many scientific and technical rea-sons. The reaction rate and selcectivity are readily tun-able by a subtle change in pressure and temperature.
: Solute molecule
O : Solvent molecule
R. Noyori,
T. Ikariya
Supercritical Fluids for Organic Synthesis
13
Methods for workup and purification of organic reaction mixtures are beginning to change as synthesis and Separation merge forces. Highly fluorinated, or fluor-ous, molecules offer a num-ber of attractive features in both traditional and parallel synthesis venues.
(FVA+B
(F) = highly fluorinated tag
©-C + D
workup
phase
Phase
D. P. Curran
Fluorous Techniques u (p)_c for the Synthesis of
Organic Molecules: A Unified Strategy for Reaction and Separation
25
Domino reactions present a modern approach in organic synthesis since they allow the preparation of complex molecules starting from simple Substrate in a few steps and in many cases with high stereoselectivity. AAoreover, as multi-component trans-formation they are highly suitable for combinatorial chemistry and give access to libraries of great diversity.
CHO
L. F. Tietze, F. Haunert
Domino Reaction in Organic Synthesis. An Approach to Efficiency, Elegance, Ecological Benefit, Economic Advantage and Preservation of Our Resources in Chemical Transformations
39
VI Table of Contents
Combinatorial chemistry has played an increasingly important role in the field of drug discovery for identifica-tion and optimization of drug leads. Combinatorial methods provide rapid access to large numbers of Compounds for testing. Shown is a general sche-matic of a combinatorial library prepared from a small set of building blocks.
* iH* ++ M O +0 O-O •-© • "*" * - # #-# • - • D +U #-D *-D 4 [4x4 = 16]
D * QO D-# OD
A. Lee,
J. W. Szewczyk, J. A. Ellman
Combinatorial I for Drug Development
65
Theoretical catalytic arrays called "theozymes" can be used to quantitate the effects of specific noncoval-ent catalyst transition State interactions on reaction rates. This strategy has been used to understand and pre-dict catalysis by both biolog-ical and synthetic catalysts.
I-
I
transition
t
State
MPMM
i n wmm , r theozyme
1
{ M M t
product
D. J. Tantillo,
K. N. Houk
Theozymes and Catalyst Design
79
Sterically and electronicaily unsymmetrical P,N-\igands have been designed to incorporate two types of coordinating units, e.g. a phosphine group and a nitrogen-containing hetero-cycle. These hybrid ligands lead to superior results in various metal-catalyzed pro-cesses and allow a system-atic 'fine tuning' of a gener-alized structure to suit a specific process.
A. C. Humphries,
A. Pfaltz
Enantioselective Catalysis using Sterically and Electronicaily Unsymmetrical Ligands
89
The successfui deveiopment of the asymmetric two-center catalysis has opened up a new field in asymmetric synthesis. It has bee especially fruitful in Michael additions and aldol reac-tions.
M. Shibasaki
Asymmetric Two-Center Catalysis
105
'~;i^n:Li§!ilp;s£;
Asymmetric phase-transfer catalysis using chiral nonra-cemic onium salts or crown ethers has now grown into a practical method whereby a large number of reactions can be performed and some optically pure Compounds can be produced effectively on a large scale.
(Reactionj Y-CH.-Z R-X, Q^X®
1
OH®, Solvent
R T. Shioiri, Y-CH-z s. Arai
Asymmetric Phase Transfer Catalysis
123
Table of Contents VII
Metal-catalyzed enantiose-lective reactions are used in the synthesis of complex organic molecules. These transformations offer cost-effective, highly selective alternatives to the more classical methods. Additional levels of efficiency are achieved when various cata-lytic reactions are used successively.
20mol% chiral
catalyst 1 cov^cov 10mol% catalyst 2
0 HO»
CT A-Q3 V-f0H
wodesntol
2mol% catalyst 3
A. H. Hoveyda
Asymmetrie Catalysis in Target-Oriented Synthesis
145
The hypothetical fullerene -acetylene hybrid at right symbolizes the exciting prospects that have arisen from the discovery of fuller-enes, and the profound changes they have induced in our view of acetylene and carbon allotrope chemistry. The preparation of molecu-lar and polymeric acetylenic carbon allotropes, as well as carbon-rich nanometer-sized struetures, has opened up new avenues in fundamental and technological research at the interface of chemistry with materials science.
Y. Rubin,
F. Diederich
From Fullerenes to Novel Carbon Allotropes: Exciting Prospects for Organic Synthesis
163
In dendrimer chemistry there are different ways to display functionalities. On the one hand, a central functional unit can be den-drylated to change some of its properties. On the other hand, it is possible to attach functional groups to the periphery of a dendrimer skeleton, i.e., the functional-ity can be multiplied.
s = functional unit
S. Gestermann,
R. Hesse, B. Windisch,
F. Vögtle
Dendritic Architectures
187
Self-assembling capsules are about to leave the play-ground of basic research and begin their career in materials sciences. The long way from the principles of self-organization through noncovalent interactions and the filling of space inside host molecules via chiral recognition and catalysis in reaction vessels to hydrogen-bonded liquid crystals and fibers forms the backbone of this review.
C. A. Schalley, J. Rebek
Chemical Encapsulation
in Self-Assembling Capsules
199
VIII Table of Contents
Kinetically stable super-architectures can be assem-bled by relying upon both noncovalent bonds and mechanical coercion. Thus, at elevated temperatures, rotaxane-like complexes (a) are generated when macro-cycles slip over the stoppers of chemical dumbbells, while hemicarceplexes (b) are created when guests squeeze through the portals of hemicarcerands.
© © M. C. T. Fyfe,
F. M. Raymo,
J. F. Stoddart
Slippage and Constrictive Binding
211
Soft and topologically adaptable supramolecular modules that allow host lat-tices to achieve dense pack-ing through low-energy deformations, while retain-ing their inherent dimen-sionality and supramolecular Connectivity, can facilitate the systematic design of molecular inclusion Compounds. This is demon-strated by the ability to pre-dict and maintain architec-tural control in a series of lamellar host frameworks.
K. T. Holman,
M. D. Ward
Crystal Engineering with Soft and Topologically Adaptable Molecular Host Frameworks
221
Synthetic routes to precisely defined molecular wires and devices are described along with procedures for testing their electronic properties. 02N^
NH2
J. M. Tour
Molecular Wires and Devices
237
The extension of the con-cepts of device and machine to the molecular level is of great scientific interest since it introduces new ideas into the field of chemistry and stimulates the ingenuity of researchers engaged in the emerging fields of nanosci-ence and nanotechnology.
molecular components
\ 1 • simple acSs
supramolecular System
^ <& Q O ^
V. Balzani,
A. Credi,
M. Venturi
Molecular-Level Devices and Machines
255
cornpiex funciion
Table of Contents IX
Long-range electron and energy transfer may take place over large distances by a through-bond or superex-change mechanism, in which the electron tunnels through the intervening medium. Examples include electron transfer through satured hydrocarbon bridges through solvent molecules and through n-stacks of base pairs in DNA.
e ET over 13.5 A
*MeO
MeO DMN DCV
CN
~CN
electron moves through c* bonds
DMN T 7 T ., DCV a and a bonds,
M. N. Paddon-Row
Electron and Energy Transfer
267
The supramolecular synthon is the supramolecular equi-valent of the functional group and is as useful in supramolecular chemistry as is the functional group in molecu-lar chemistry. Synthons are small repetitive units that economically, yet fully, cap-ture the essence of a crystal structure.
^ ; Synthoi
G. R. Desiraju
The Supramolecular Synthon in Crystal Engineering
293
Connecting lumophores and receptors with spacers per-mits the build-up of modular Systems of increasing logical complexity. Even the sim-plest of these Systems can be powerful molecular sensors. Light Power Light Output Chemicai input
A. P. de Silva, D. B. Fox, T. S. Moody
Luminescent Logic and Sensing
307
Nanochemistry creates new opportunities for chemistry, since molecular characteris-tics are obtained which no longer resemble an ensemble average. The task of nanochemistry is to provide an insight into structure and function at a molecular level.
S. Becker, K. Müllen
Nanochemistry -Architecture at the Mesoscale
317
This chapter focuses on mimics based on natural enzymes and other biopoly-mers, synthetic macromole-cules and small-molecule host-guest interactions.
N I M M Pu-PyHM
ff I I • H P y U Ar""1
r G G
C C
TA J G C T A C
5'-ribo
3'-deoxyribo
A. J. Kirby
Enzyme Mimics
341
Recent developments in enzyme inhibitor design are reviewed, with particular emphasis on the "distal binding analog" approach.
distal binding Site
I Enzyme
active site
• Enzyme-Inhibitor Complex
K. D. Kreutter, C.-H. Wong
Asymmetrie Two-Enzyme Inhibitors
355
X Table of Contents
This chapter highlights the interplay between organic synthesis, biophysics and cell biology in the study of protein lipidation and its rel-evance to targeting proteins towards the plasma mem-brane of cells in precise molecular detail.
D. Kadereit, J. Kuhlmann, H. Waldmann
Organic Synthesis and Cell Biology
369
Biopbysical Chemisuy Molecular Biologv
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