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Current Organic Chemistry
ISSN: 1385-2728
Current Organic
Chemistry
Volume 10, Number 2, January 2006
Contents
Ruthenium Catalyzed Processes
Guest Editor: José Gimeno
Editorial Pp. 113
η3-Allylruthenium
Complexes and Ruthenium-Catalyzed Nucleophilic Substitution
of Allylic Substrates Pp. 115-133
Jean-Luc Renaud, Bernard Demerseman, Mbaye Diagne Mbaye and Christian Bruneau
[Abstract]
Ruthenium-Catalyzed Novel Carbon-Carbon Bond Forming
Reactions via Ruthenium-Allenylidene Complexes
Pp. 135-150
Yoshiaki Nishibayashi and Sakae Uemura
[Abstract]
Lewis Acid Catalysis by Ruthenium Complexes
Pp. 151-163
Jack Faller and Jonathan Parr
[Abstract]
Bis(allyl)-Ruthenium(IV) Complexes: Promising Precursors
for Catalytic Organic Synthesis Pp. 165-183
Victorio Cadierno, Pascale Crochet, Sergio E. García-Garrido
and José Gimeno
[Abstract]
Ruthenium-Catalyzed Ring-Closing Metathesis: Recent
Advances, Limitations and Opportunities Pp.
185-202
Jay C. Conrad and Deryn E. Fogg
[Abstract]
Synthesis and Application of New N-Heterocyclic Carbene
Rurthenium Complexes in Catalysis: A Case Study Pp.
203-215
Lionel Delaude, Albert Demonceau and Alfred F. Noels
[Abstract]
Ruthenium Catalysts for the Kharasch Reaction
Pp. 217-224
Kay Severin
[Abstract]
Ruthenium Complexes with Chiral Tetradentate PNNP
Ligands in Asymmetric Catalytic Atom-Transfer Reactions
Pp. 225-240
Cristina Bonaccorsi and Antonio Mezzetti
[Abstract]
Design of Ruthenium Catalysts Bound to Inorganic Crystalline
Materials for Environmentally-Benign Organic Synthesis Pp.
241-255
Kiyotomi Kaneda, Kohsuke Mori, Tomoo Mizugaki and Kohki
Ebitani
[Abstract]
Abstracts
[Back to top]
Editorial
Applications of organo-ruthenium derivatives in homogeneous
catalysis have disclosed one of the cornerstones in the spectacular
development of Organometallic Chemistry during the last decade.
The special ability of ruthenium complexes to form a wide
range of inorganic and organometallic complexes, featuring
a wide scope of oxidation states, several coordination geometries
and reactivity patterns, has triggered a growing interest.
Nowadays, they may be considered, in a wide number of chemical
transformations, as very competitive alternatives to other
classical transition metal catalysts such as palladium, rhodium,
platinum etc. giving rise, indeed, to a very appealing field
of research.
The present issue of Current Organic Chemistry entitled “Ruthenium
Catalyzed Processes” deals with a series of nine articles
from expert authors in the field illustrating recent developments
of the usefulness in organic synthesis. The articles show
the state of the art of specific aspects as well as complement
important issues not covered by recent reviews or monographs
on their catalytic applications The contributions highlight
the progress of the catalytic activity in novel C-C bond forming
reactions including allylic activation (C. Bruneau and co-workers),
propargylic alcohol substitutions, (Y. Nishibayashi and S.
Uemura) and other type involving Lewis acid catalysis (J.
Faller and J. Parr). In their article J. Gimeno and co-workers
summarize the chemistry of bis-allyl ruthenium(IV) derivatives
and their catalytic applications in, among other reactions,
polymerization of olefins, transfer hydrogenation of ketones
and isomerization of allylic alcohols in water. Two articles
dealing with Ring-closing metathesis (D.E. Fogg and J.C. Conrad)
and applications of novel N-heterocyclic carbene-ruthenium
complexes (A.F. Noels and co-workers) give further details
on the well-known catalytic applications of carbene ruthenium
complexes. The catalytic activity of ruthenium complexes in
reactions involving transfer of atoms through radical additions
such as Kharash reactions (K. Severin) and asymmetric atom-transfer
reactions (C. Bonaccorsi and A. Mezzetti), illustrates the
ability to catalyze this relatively less studied type of processes.
Finely, the article from K. Kaneda and co-workers reviews
the catalytic activity of immobilized-ruthenium complexes
showing the promising applications of heterogeneous ruthenium
catalysts in the development of a sustainable chemistry.
I thank all the authors for their valuable reviews which
I hope will be helpful to many organic chemists interested
in innovative and non-classical chemical transformations.
José Gimeno
Departamento de Química Orgánica e Inorgánica,
Instituto de Química Organometálica "Enrique
Moles"
Facultad de Química, Universidad de Oviedo,
E-33071 Oviedo,
Spain
[Back to top]
η3-Allylruthenium
Complexes and Ruthenium-Catalyzed Nucleophilic Substitution
of Allylic Substrates
Jean-Luc Renaud, Bernard Demerseman, Mbaye Diagne Mbaye and Christian Bruneau
Recent developments in the chemistry of η3-allylruthenium
complexes (synthesis and reactivity) are described. Among
different possible preparations, their straightforward formation
via oxidative addition of allylic substrates occurs
either at ruthenium(0) or ruthenium(II) centres. Subsequent
reaction with an electrophile or a nucleophile is the basis
of their ambiphilic involvement in catalysis. In this review,
we focus on catalytic substitution of allylic substrates by
C, N, O and S nucleophiles, and show that
selected ligands make possible stereospecific, as well as
regio- and enantioselective substitutions.
[Back to top]
Ruthenium-Catalyzed Novel Carbon-Carbon Bond Forming
Reactions via Ruthenium-Allenylidene Complexes
Yoshiaki Nishibayashi and Sakae Uemura
Our recent studies on novel carbon-carbon bond forming reactions
using propargylic alcohols catalyzed only by thiolate-bridged
diruthenium complexes are reviewed from the viewpoint of organic
synthesis. The reactions are substitutions of hydroxyl group
of the alcohols with a variety of carbon-centered nucleophiles
such as simple ketones, cyclic 1,3-dicarbonyl compounds, aromatic
and heteroaromatic compounds, phenols, naphthols, and alkenes.
The asymmetric version of propargylic alkylation with acetone
is also described. All of the reactions are considered to
proceed via ruthenium-allenylidene complexes as key intermediates.
[Back to top]
Lewis Acid Catalysis by Ruthenium Complexes
Jack Faller and Jonathan Parr
Recent progress in the Lewis acid catalysis of organic reactions
by ruthenium complexes. The review focuses on reactions in
which coordinatively unsaturated ruthenium species function
as conventional Lewis acids, rather than those involving oxidation
or reduction, such as in hydrogenations. Particular emphasis
is placed on the development of asymmetric catalysts.
[Back to top]
Bis(allyl)-Ruthenium(IV) Complexes: Promising Precursors
for Catalytic Organic Synthesis
Victorio Cadierno, Pascale Crochet, Sergio E. García-Garrido
and José Gimeno
The present review reports on the chemistry of the bis(allyl)-ruthenium(IV)
complexes [{Ru(η3:η3-C10H16)(μ-Cl)Cl}2]
(C10H16 = 2,7-dimethylocta-2,6-diene-1,8-diyl)
and [Ru(η3:η2:η3-C12H18)C2]
(C12H18 = dodeca-2,6,10-triene-1,12-diyl).
Stoichiometric reactions allowing the preparation of a variety
of organoruthenium(IV) and (II) derivatives, as well as the
involvement of these species in a series of catalytic organic
transformations are presented.
[Back to top]
Ruthenium-Catalyzed Ring-Closing Metathesis: Recent
Advances, Limitations and Opportunities
Jay C. Conrad and Deryn E. Fogg
Recent advances in ruthenium-catalyzed ring closing metathesis
are discussed, in context of both substrate and catalyst parameters.
As well as thermodynamic (substrate) constraints on ring-closing,
root causes and effects of non-ideal catalytic performance
are examined. Key substrate parameters are outlined, with
a particular focus on the balance between oligomerization
and ring-closing in RCM macrocyclization reactions. Advances
in catalyst design are examined from a mechanistic viewpoint,
including initiation requirements, catalyst deactivation,
and opportunities resulting from incorporation of pseudohalide
ligands. An overview of methods for reducing ruthenium residues
in organic products to ppm levels is presented.
[Back to top]
Synthesis and Application of New N-Heterocyclic
Carbene Rurthenium Complexes in Catalysis: A Case Study
Lionel Delaude, Albert Demonceau and Alfred F. Noels
New imidazolium and imidazolinium salts were synthesized
and their ability to act as stable N-heterocyclic
carbene (NHC) ligand precursors was investigated in various
ruthenium-catalyzed processes. Thus, 1,3-diarylimidazol(in)ium
chlorides bearing the phenyl, 1-naphthyl, 4 biphenyl, 3,5-dimethylphenyl,
2-tolyl, 2,6-dimethylphenyl, 2,4,6-trimethylphenyl (mesityl),
and 2,6-diisopropylphenyl substituents were prepared. They
were combined with the [RuCl2(p cymene)]2
dimer and potassium tert-butoxide or sodium hydride
to generate the corresponding ruthenium-arene complexes [RuCl2(p-cymene)(NHC)]
in situ. The catalytic activity of all these species
was investigated in the photoinduced ring-opening metathesis
polymerization (ROMP) of norbornene and cyclooctene. Results
from this study showed that the C4-C5 double bond in the imidazole
ring of the NHC ligands was not crucial to achieve high catalytic
efficiencies. The presence or the absence of alkyl groups
on the ortho positions of the phenyl rings had a
more pronounced influence. Blocking all the ortho
positions was a requisite for obtaining efficient catalysts.
Failure to do so probably resulted in the ortho-metallation
of the carbene ligand, thereby altering the coordination sphere
of the ruthenium active centers. Catalytic screenings were
also carried out with the various imidazol(in)ium salts to
evaluate their ability at promoting the cyclopropanation of
styrene and cyclooctene with ethyl diazoacetate. Under the
experimental conditions adopted, the exact nature of the
N,N'-diaryl groups had very little influence on the outcome
of these reactions. The imidazolium salts were further probed
as catalyst modifiers for the Atom Transfer Radical Addition
(ATRA) of carbon tetrachloride to styrene. Some species displayed
a dual activity and promoted both olefin metathesis and ATRA.
[Back to top]
Ruthenium Catalysts for the Kharasch Reaction
Kay Severin
Recent advances in the development of ruthenium catalysts
for the atom transfer radical addition of polyhalogenated
compounds to olefins ('Kharasch reaction') are described.
Three classes of homogeneous catalysts are discussed: halfsandwich
complexes with
η6-arene,
η5-cyclopentadienyl or
η5-carborane ligands, ruthenium complexes
with alkylidene- or vinylidene ligands and polynuclear complexes.
Furthermore, first attempts to use immobilized ruthenium complexes
as heterogeneous catalysts for the Kharasch reaction are summarized.
[Back to top]
Ruthenium Complexes with Chiral Tetradentate PNNP
Ligands in Asymmetric Catalytic Atom-Transfer Reactions
Cristina Bonaccorsi and Antonio Mezzetti
This account describes the application of ruthenium complexes
containing chiral tetradentate ligands PNNP, featuring a P2N2
ligand set as catalysts for enantioselective reactions involving
atom-transfer between the metal complex and a non-coordinated
molecule. The five-coordinate 16-electron [RuCl(PNNP)]+
species and their octahedral analogues [RuCl(L)(PNNP)]+
have been used in the asymmetric epoxidation and cyclopropanation
of olefins, in which oxene or carbene are transferred from
ruthenium to the noncoordinated substrate. The [RuCl(PNNP)]+
catalysts cyclopropanate styrenes and 1-octene in the presence
of ethyl diazoacetate with excellent cis- and enantioselectivity.
By means of anion optimization and electronic tuning of the
PNNP ligand, we achieved the highly cis-selective
cyclopropanation of 1-octene, which is, to the best of out
knowledge, the first example for a terminal aliphatic olefin.
A different mode of enantioselective atom transfer has been
observed in the hydroxylation and electrophilic fluorination
of 1,3-dicarbonyl compounds, in which the oxene or F+-transfer
agent attacks a ruthenium-bound substrate. This mechanism
is supported by stoichiometric reactions with the isolated
enolato complexes formed upon reaction with activated ruthenium
species obtained by double chloride abstraction from [RuCl2(PNNP)]
with Et3OPF6. Nucleophilic fluorination
of activated haloalkanes is also reported.
[Back to top]
Design of Ruthenium Catalysts Bound to Inorganic Crystalline
Materials for Environmentally-Benign Organic Synthesis
Kiyotomi Kaneda, Kohsuke Mori, Tomoo Mizugaki and Kohki
Ebitani
This article reviews a novel approach to design heterogeneous
Ru catalysts using hydroxyapatites and hydrotalcites, and
their excellent catalytic performances for aerobic alcohol
oxidations, carbon–carbon bond formations, and one-pot
syntheses. The catalytic systems using the above heterogeneous
Ru catalysts offer significant benefits in achieving simple
and clean organic syntheses. Furthermore, the present preparation
method for the immobilization of metal species is much simpler
than previous synthetic methods of the solid-supported transition
metal catalysts, which can allow a strong protocol to create
various nanostructured and functionalized heterogeneous metal
catalysts.
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