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Current Organic Synthesis
ISSN: 1570-1794
Current Organic Synthesis
Volume 4, Number 4, November 2007
Contents
Synthesis in Ionic Liquids
Guest Editor: Kenneth K. Laali
Editorial Pp. 252
About the Editor Pp. 353
Enzyme Mediated Reactions in Ionic Liquids
Pp. 354-369
J.R. Harjani, P.U. Naik, S.J. Nara and M.M. Salunkhe
[Abstract]
Asymmetric Catalysis in Ionic Liquids Pp.
370-380
Sanjay V. Malhotra, Vineet Kumar and Virinder S. Parmar
[Abstract]
The Chemistry of the C2 Position of Imidazolium Room
Temperature Ionic Liquids Pp. 381-389
Elliot Ennis and Scott T. Handy
[Abstract]
Regular Articles
Transition Metal Complexes of Some Azamacrocycles and Their
Use in Molecular Recognition Pp. 390-412
Jens Geduhn, Thomas Walenzyk and Burkhard König
[Abstract]
Recent Progress in the Chemistry of Allenes
Pp. 413-439
Hammed H.A.M. Hassan
[Abstract]
Abstracts
[Back to top]
Editorial: Synthesis in Ionic Liquids
Application of ionic liquids (ILs) in synthesis continues
to experience astonishing growth.
The realization that physical and chemical properties of the
ILs can be tailored by judicious selection of the cation and
anion structures, has undoubtedly contributed to the enthusiasm
by the synthetic chemistry community to exploit these alternative
media for a wide variety of organic and organometallic transformations,
not only as environmentally more acceptable/green alternatives
to conventional volatile organic solvents (VOS), but also
as Lewis and protic acid catalysts. The recovery and recycling
aspects have also had a tremendous impact on the field, in
a worldwide effort to switch from VOS to ILs.
Application of ILs in the area of catalysis, in particular
in biocatalysis and asymmetric catalysis are two of most recently
emerging and promising areas in IL chemistry. Since both of
these developing areas have focused strongly on the use of
imidazolium-based ILs, this brings out an important issue
concerning the acidity of C2
position on the imidazolium ring, which could generate N-heterocyclic
carbenes with relative ease. This aspect needs to be taken
into consideration when performing base-catalyzed transformations
in these media, as it could open up unwanted reaction channels
involving the IL itself!
In relation to the above, the three review articles selected
for this special issue of COS are devoted to biocatalysis
(enzyme-mediated), asymmetric catalysis, and to the chemistry
of the C2 position of the
imidazolium ILs respectively:
i) M. M. Salunkhe and associates (Institute of Scienec, Mumbai)
discuss and analyze the developments achieved over the course
of the last decade in enzyme-mediated reactions in ILs. It
has been shown that enzymes are stabilized in certain ILs
and could be irreversibly activated by incubation in the ILs.
ii) S. J. Malhotra and coworkers (New Jersey Institute of
Technology) summarize the progress made during recent years
in the area of asymmetric catalysis in ILs, employing organometallics
and organocatalysts.
iii) E. Ennis and S. T. Handy (Middle Tennessee State University)
focus on the issue of C2
acidity in the imidazolium ILs, and draw attention to the
deprotonation path as a potential side reaction in certain
transformations such as the Baylis-Hillman and Negishi-type
coupling reactions. They also discusses methods available
so far for the synthesis of C2
substituted imidazolium-ILs, in an effort to avid these potential
side reactions.
As an advisory board member for COS and the executive editor
for this special issue I would like to acknowledge and to
thank the contributors for their efforts to provide timely
review summaries and to analyze the current state of affair
in these areas.
Kenneth K. Laali
Department of Chemstry,
Kent State University,
Kent. OH 44242,
USA
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About the Editor
Kenneth Laali did his PhD work (1974-1977) at the University
of Manchester (with R. N. Haszeldine and B. L. Booth). A postdoctoral
stint with the late Victor Gold at King’s College (1977-1979)
was followed by appointments in Strasbourg (with J. Sommer),
Amsterdam (with H. Cerfontain) and at ETH-Zurich (with H.
Zollinger). In 1982 he joined George Olah’s group at
the University of Southern California, and in 1985 began his
independent academic career at Kent State University, where
he went through the ranks, becoming full professor in 1996.
Research in the Laali laboratory focuses on multifaceted projects
that combine synthetic, physical organic (structural/mechanistic
and spectroscopic) and theoretical approaches to solving diverse
problems in organic chemistry. Since 2000, he has been actively
pursuing projects on synthetic and mechanistic studies in
ionic liquids, where interest is mainly focused on electrophilic
chemistry involving carbocations and onium ions. Ken Laali
has so far authored and coauthored over 150 publications and
4 books.
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Enzyme Mediated Reactions in Ionic Liquids
J.R. Harjani, P.U. Naik, S.J. Nara and M.M. Salunkhe
The virtues associated with use of ionic liquids for enzyme-mediated
reactions make them promising alternatives to the conventional
reaction media. The scope of this review includes the developments
witnessed by the area of the biotransformations in ionic liquids
over more than a decade, presenting the pros and cons associated
with the use of these novel ionic media.
[Back to top]
Asymmetric Catalysis in Ionic Liquids
Sanjay V. Malhotra, Vineet Kumar and Virinder S. Parmar
Ionic Liquids are becoming increasingly attractive as alternative
media for organic synthesis. Strategies such as the use of
biocatalysts, chiral ionic liquids, chiral reagent and/or
catalysts, have been employed to achieve asymmetric transformations
in ionic liquids. The focus of this review is on the developments
made in asymmetric catalysis using organometallic and organocatalysts
in ionic liquids.
[Back to top]
The Chemistry of the C2 Position of Imidazolium Room
Temperature Ionic Liquids
Elliot Ennis and Scott T. Handy
Among room temperature ionic liquids (RTILs), those derived
from imidazole are the most common. They are generally viewed
solely as solvents, but can participate in certain types of
chemistry particularly due to the relatively high acidity
at C2. Deprotonation affords N-heterocyclic carbenes
(NHCs). This chemistry, and potential means of avoiding it,
are discussed as are the use of NHCs in the preparation of
new RTILs.
[Back to top]
Transition Metal Complexes of Some Azamacrocycles and Their
Use in Molecular Recognition
Jens Geduhn, Thomas Walenzyk and Burkhard König
Azamacrocycles show high affinity for the complexation of
a wide range of transition metals. By additional reversibly
coordinated ligands, these metal complexes have shown to be
interesting tools for molecular recognition, especially for
biological systems. Herein, the role of metal complexes of
1,4,8,11-tetraaza-cyclotetradecane ([14]aneN4
or cyclam), 1,4,7,10-tetraaza-cyclododecane ([12]aneN4
or cyclen), 1,5,9-triaza-cyclododecane ([12]aneN3),
1,4,7-triaza-cyclononane ([9]aneN3
or TACN) is reviewed.
[Back to top]
Recent Progress in the Chemistry of Allenes
Hammed H.A.M. Hassan
Allenes are important compounds in organic and synthetic organic
chemistry and therefore a large number of studies on their
synthesis and reactions have been reported so far. We report
the most recent methods for the synthesis of allenes, including
optically active forms and fluorinated and gem-difluorinated
allenes, in this paper. Reactions such as nucleophilic addition
of allenes were classified and discussed in details according
to the nature of the nucleophile either oxygen, nitrogen,
carbon or sulfur, whereas, inter- and intra-molecular cycloadditions
reactions with a variety of unsaturated functionality were
separately discussed. A collection of some useful reactions
such as coupling reactions of allenes mediated by organometallic
reagents, intramolecular cyclization of allenes with tethered
amines, asymmetric dihydroxylation, and epoxidation of allenes
are also included.
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