References of "Demonceau, Albert"
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See detailRecent Advances in Ruthenium Catalysts for Alkene Metathesis
Delaude, Lionel ULg; Demonceau, Albert ULg; Dragutan, Ileana et al

in Demonceau, Albert; Dragutan, Ileana; Finkelshtein, Eugene Sh. (Eds.) et al Green Metathesis Chemistry (2010)

Although ruthenium initiators currently available for alkene metathesis are endowed with many beneficial properties, there is still room for improvement and many research groups are actively pursuing the ... [more ▼]

Although ruthenium initiators currently available for alkene metathesis are endowed with many beneficial properties, there is still room for improvement and many research groups are actively pursuing the quest for the next generation of alkene metathesis catalysts. The present contribution aims at providing a critical survey of some of the most significant achievements accomplished toward this goal during the last few years. New ligands and complexes designed to achieve the appropriate balance between electronic and steric properties of the ruthenium active centres are depicted, and their stability, activity, and chemoselectivity are briefly discussed. [less ▲]

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See detailRuthenium—Arene Complexes Derived from NHC∙CO2 and NHC∙CS2 Zwitterionic Adducts and Their Use in Olefin Metathesis
Delaude, Lionel ULg; Demonceau, Albert ULg

in Dragutan, Valerian; Demonceau, Albert; Dragutan, Ileana (Eds.) et al Green Metathesis Chemistry (2010)

A range of imidazol(in)ium-2-carboxylates and -dithiocarboxylates bearing alkyl or aryl groups on their nitrogen atoms were prepared by reacting the corresponding N-heterocyclic carbenes (NHCs) with ... [more ▼]

A range of imidazol(in)ium-2-carboxylates and -dithiocarboxylates bearing alkyl or aryl groups on their nitrogen atoms were prepared by reacting the corresponding N-heterocyclic carbenes (NHCs) with either carbon dioxide or carbon disulfide. All the zwitterionic products were characterized by various analytical techniques, including thermogravimetric analysis (TGA). Their ability to act as NHC ligand precursors for in situ catalytic applications was investigated in the ruthenium-promoted ring-opening metathesis polymerization (ROMP) of cyclo-octene. Upon exposure to the [RuCl2(p-cymene)]2 dimer, the NHC CO2 adducts readily dissociated to generate [RuCl2(p-cymene)(NHC)] complexes that were highly active catalyst precursors for olefin metathesis. Conversely, the NHC CS2 betaines retained their zwitterionic nature and led to new cationic complexes of the [RuCl(p-cymene)(NHC CS2)]+PF6 − type that were devoid of any significant catalytic activity in the reaction under consideration [less ▲]

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See detailTandem catalysis of ring-closing metathesis/atom transfer radical reactions with homobimetallic ruthenium-arene complexes
Borguet, Yannick ULg; Sauvage, Xavier ULg; Zaragoza, Guillermo et al

in Beilstein Journal of Organic Chemistry (2010), 6

The tandem catalysis of ring-closing metathesis/atom transfer radical reactions was investigated with the homobimetallic ruthenium-indenylidene complex [(p-cymene)Ru(mu-Cl)(3)RuCl(3-phenyl-1-indenylidene ... [more ▼]

The tandem catalysis of ring-closing metathesis/atom transfer radical reactions was investigated with the homobimetallic ruthenium-indenylidene complex [(p-cymene)Ru(mu-Cl)(3)RuCl(3-phenyl-1-indenylidene)(PCy3)] (1) to generate active species in situ. The two catalytic processes were first carried out independently in a case study before the whole sequence was optimized and applied to the synthesis of several polyhalogenated bicyclic gamma-lactams and lactones from alpha,omega-diene substrates bearing trihaloacetamide or trichloroacetate functionalities. The individual steps were carefully monitored by H-1 and P-31 NMR spectroscopies in order to understand the intimate details of the catalytic cycles. Polyhalogenated substrates and the ethylene released upon metathesis induced the clean transformation of catalyst precursor 1 into the Ru(II)-Ru(III) mixed-valence compound [(p-cymene) Ru(mu-Cl)(3)RuCl2(PCy3)], which was found to be an efficient promoter for atom transfer radical reactions under the adopted experimental conditions. [less ▲]

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See detailNovel, Highly Efficient and Selective Ruthenium Catalysts for the Synthesis of Vinyl Esters from Carboxylic Acids and Alkynes
Nicks, Francois ULg; Aznar, Rozario; Sainz, Daniel et al

in European Journal of Organic Chemistry (2009), 2009(29), 5020-5027

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See detailATRP of Methacrylates Catalysed by Homo- and Heterobimetallic Ruthenium Complexes
Borguet, Yannick ULg; Sauvage, Xavier; Bicchielli, Dario ULg et al

in Matyjaszewski, Krzysztof (Ed.) Controlled/Living Radical Polymerization: Progress in ATRP (2009)

The catalytic activity of a series of ruthenium-based homo- and heterobimetallic complexes was determined by investigating the atom transfer radical polymerisation of methyl methacrylate. The complexes ... [more ▼]

The catalytic activity of a series of ruthenium-based homo- and heterobimetallic complexes was determined by investigating the atom transfer radical polymerisation of methyl methacrylate. The complexes under investigation were [(arene)Ru(µ-Cl)3RuCl(C2H4)-(L)] (L = PCy3 or a N-heterocyclic carbene ligand), [(p-cymene)-Ru(µ-Cl)3RuCl(=C=CHR)(PCy3)] (R = Ph or t-Bu), and [RuCl2-(p-cymene){PCy2(CH2)2(eta5-C5H4)TiX2(eta5-C5H5)}] (X = Cl, F, and OBz). The catalytic activity of a variety of related [(p-cymene)-ClRu(µ-Cl)2Ru(O‚^N)(=CHPh)] complexes (O^N is a Schiff base ligand) is also reported. The results clearly demonstrate that the ligands strongly affect the ability of the resulting ruthenium complexes to favour the occurrence of a well-behaved ATRP. [less ▲]

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See detailMicrowave-Assisted Ruthenium-Catalyzed Reactions
Nicks, Francois ULg; Borguet, Yannick ULg; Delfosse, Sebastien et al

in Australian Journal of Chemistry (2009), 62(3), 184-207

Since the first reports on the use of microwave irradiation to accelerate organic chemical transformations, a plethora of papers has been published in this field. In most examples, microwave heating has ... [more ▼]

Since the first reports on the use of microwave irradiation to accelerate organic chemical transformations, a plethora of papers has been published in this field. In most examples, microwave heating has been shown to dramatically reduce reaction times, increase product yields, and enhance product purity by reducing unwanted side reactions compared with conventional heating methods. The present contribution aims at illustrating the advantages of this technology in homogeneous catalysis by ruthenium complexes and, when data are available, at comparing microwave-heated and conventionally heated experiments. Selected examples refer to olefin metathesis, isomerization reactions, 1,3-dipolar cycloadditions, atom transfer radical reactions, transfer hydrogenation reactions, and H/D exchange reactions. [less ▲]

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See detailExploring new achievements in olefin metathesis catalysts. Part 2 - Compelling innovations in ruthenium complexes
Dragutan, Ileana; Dragutan, Valerian; Delaude, Lionel ULg et al

in Chimica Oggi = Chemistry Today (2009), 27(3), 13-16

This part of the survey introduces recent developments on de novo designed types of ruthenium complexes used as promoters in olefin metathesis reactions. Encompassing diversity-oriented initiators not ... [more ▼]

This part of the survey introduces recent developments on de novo designed types of ruthenium complexes used as promoters in olefin metathesis reactions. Encompassing diversity-oriented initiators not illustrated in Part 1, in this second part of the review emphasis is placed on the leading role played by distinct ligands in an exquisite control of metathesis reactions. [less ▲]

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See detailExploring New Achievements in olefin metathesis catalysts. Part 1 - Highlights on N-heterocyclic carbene ruthenium complexes
Dragutan, Valerian; Dragutan, Ileana; Delaude, Lionel ULg et al

in Chimica Oggi = Chemistry Today (2009), 27(3), 9-12

Most important advances in ruthenium catalysts for olefin metathesis achieved during the last 4 years are briefly reviewed. The first part of the survey focuses on new catalytic precursors endowed with ... [more ▼]

Most important advances in ruthenium catalysts for olefin metathesis achieved during the last 4 years are briefly reviewed. The first part of the survey focuses on new catalytic precursors endowed with inventive N-heterocyclic carbene ligands which have proved highly proficient in a diversity of applications based on metathesis reactions. Part two extends the progress in other types of Ru initiators. [less ▲]

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See detailRuthenium-arene complexes bearing imidazol(in)ium-2-dithiocarboxylate ligands: Evaluation of their catalytic activity in the synthesis of enol esters
Willem, Quentin ULg; Nicks, Francois ULg; Sauvage, Xavier et al

in Journal of Organometallic Chemistry (2009), 694(25), 4049-4055

The catalytic activity of four ruthenium imidazol(in)ium-2-dithiocarboxylates was evaluated for the synthesis of vinyl esters through addition of 4-acetoxybenzoic acid to 1-hexyne, and compared to those ... [more ▼]

The catalytic activity of four ruthenium imidazol(in)ium-2-dithiocarboxylates was evaluated for the synthesis of vinyl esters through addition of 4-acetoxybenzoic acid to 1-hexyne, and compared to those of the parent ruthenium-N-heterocyclic carbene complexes and [RuCl2(p-cymene)(PPh3)] (a standard catalyst). It turned out that ruthenium imidazol(in)ium-2-dithiocarboxylates were poorly active and selective. Quantitative yields, indeed, were obtained only after extended reaction times. However, the catalytic activity could be improved significantly under microwave heating or conventional heating in a sealed tube at 160 degrees C, driving the reaction to completion in less than 4 h of reaction. [less ▲]

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See detailAssessing the Potential of Zwitterionic NHC•CS2 Adducts for Probing the Stereoelectronic Parameters of N-Heterocyclic Carbenes
Delaude, Lionel ULg; Demonceau, Albert ULg; Wouters, Johan

in European Journal Of Inorganic Chemistry (2009), (13), 1882-1891

Five imidazol(in)ium-2-dithiocarboxylates bearing cyclohexyl, mesityl, or 2,6-diisopropylphenyl substituents on their nitrogen atoms were prepared from the corresponding N-heterocyclic carbenes (NHCs) by ... [more ▼]

Five imidazol(in)ium-2-dithiocarboxylates bearing cyclohexyl, mesityl, or 2,6-diisopropylphenyl substituents on their nitrogen atoms were prepared from the corresponding N-heterocyclic carbenes (NHCs) by reaction with carbon disulfide. They were characterized by IR, UV/Vis, and NMR spectroscopy, and by thermogravimetric analysis. Their molecular structures were determined by X-ray diffraction. For the sake of comparison, tricyclohexylphosphonium dithiocarboxylate was also examined. The data acquired were scrutinized to evaluate their usefulness for assessing the steric and electronic properties of NHC ligands. Because of their outstanding ability to crystallize, the five NHC center dot CS2 betaines were found to be highly suitable for probing the steric influence of nitrogen atom substituents on imidazolylidene-based ligand precursors via XRD analysis, while the corresponding NHC center dot CO2 adducts were deemed more appropriate for evaluating the sigma-donating properties of carbene ligands. ((c) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009) [less ▲]

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See detailMicrowave-Assisted Synthesis of Vinyl Esters through Ruthenium-Catalyzed Addition of Carboxylic Acids to Alkynes
Nicks, Francois ULg; Libert, Lionel ULg; Delaude, Lionel ULg et al

in Australian Journal of Chemistry (2009), 62(3), 227-231

A rapid and efficient method is described for the selective synthesis of enol esters via the microwave-accelerated addition of carboxylic acids to terminal alkynes. The method employs the readily ... [more ▼]

A rapid and efficient method is described for the selective synthesis of enol esters via the microwave-accelerated addition of carboxylic acids to terminal alkynes. The method employs the readily available [RuCl2(p-cymene)(PPh3)] complex as catalyst without the need of bases, and reactions are complete in 20 min. [less ▲]

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See detailHomobimetallic Ruthenium Vinylidene, Allenylidene, and Indenylidene Complexes: Synthesis, Characterization, and Catalytic Studies
Sauvage, Xavier ULg; Borguet, Yannick ULg; Zaragoza, Guillermo et al

in Advanced Synthesis & Catalysis (2009), 351(3), 441-455

Four homobimetallic ruthenium-(p-cymene) complexes bearing a tricyclohexylphosphine ligand and polyunsaturated carbon-rich fragments were obtained via a vinylidene-allenylidene-indenylidene cascade ... [more ▼]

Four homobimetallic ruthenium-(p-cymene) complexes bearing a tricyclohexylphosphine ligand and polyunsaturated carbon-rich fragments were obtained via a vinylidene-allenylidene-indenylidene cascade pathway from the ethylene complex [(p-cymene)Ru(mu-Cl)(3)RuCl(PCy3)(eta(2)-C2H4)] (7a). All the products were isolated and fully characterized by IR and NMR spectroscopies. The molecular structure of the indenylidene complex 11 was determined by X-ray crystallographic analysis. The catalytic activity of the four complexes was probed in various types of olefin metathesis reactions and compared with those of a related homobimetallic ruthenium-benzylidene complex, as well as first, second, and third generation monometallic Grubbs catalysts. In the ring-closing metathesis (RCM) of diethyl diallylmalonate, the homobimetallic ruthenium-indenylidene complex 11. outperformed all the ruthenium-benzylidene complexes under investigation and was only slightly less efficient than its monometallic parent. Cross-metathesis experiments with ethylene showed that deactivation of ruthenium-benzylidene or indenylidene complexes was due to the rapid bimolecular decomposition of methylidene active species into ethylene complex 7a. Vinylidene and allenylidene complexes were far less efficient catalyst precursors for ring-opening metathesis polymerization (ROMP) or RCM and remained inert under an ethylene atmosphere. Their catalytic activity was, however, substantially enhanced upon addition of an acidic co-catalyst that most likely promoted their in situ transformation into indenylidene species. Due to its straightforward synthesis and high metathetical activity, homobimetallic ruthenium-indenylidene complex 11 is a valuable intermediate for the preparation of the Hoveyda-Grubbs catalyst [Cl2Ru(PCy3)(=CH-o-O-i-PrC6H4)] via stoichiometric cross-metathesis with 2-isopropoxystyrene. ne procedure did not require any sacrificial phosphine and the transition metal not incorporated into the final product was easily recovered and recycled at the end of the process. [less ▲]

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See detailImidazol(in)ium-2-carboxylates as N-heterocyclic carbene precursors for the synthesis of second generation ruthenium metathesis catalysts
Sauvage, Xavier ULg; Demonceau, Albert ULg; Delaude, Lionel ULg

in Advanced Synthesis & Catalysis (2009), 351(11-12), 2031-2038

Five well-known ruthenium-N-heterocyclic carbene (NHC) catalysts for olefin metathesis and related reactions, including the second generation Grubbs and Hoveyda-Grubbs catalysts, were prepared by ... [more ▼]

Five well-known ruthenium-N-heterocyclic carbene (NHC) catalysts for olefin metathesis and related reactions, including the second generation Grubbs and Hoveyda-Grubbs catalysts, were prepared by phosphane exchange between first generation ruthenium-benzylidene or indenylidene complexes and NHCs generated in situ upon thermolysis of imidazol(in)ium-2-carboxylates. Because N-heterocyclic carbene -carbon dioxide adducts (NHC · CO2) are stable zwitterionic compounds that can be stored and handled with no particular precautions, this procedure is particularly attractive from a practical point of view. Reaction courses were conveniently monitored by 31P NMR spectroscopy and the experimental conditions were carefully adjusted to obtain high yields of pure products within short periods of time. [less ▲]

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See detailSynthesis and Catalytic Evaluation of Ruthenium-Arene Complexes Generated Using Imidazol(in)ium-2-carboxylates and Dithiocarboxylates
Delaude, Lionel ULg; Sauvage, Xavier ULg; Demonceau, Albert ULg et al

in Organometallics (2009), 28

The ability of five imidazol(in)ium-2-carboxylates and dithiocarboxylates bearing cyclohexyl, mesityl, or 2,6-diisopropylphenyl substituents on their nitrogen atoms to act as NHC precursors for in situ ... [more ▼]

The ability of five imidazol(in)ium-2-carboxylates and dithiocarboxylates bearing cyclohexyl, mesityl, or 2,6-diisopropylphenyl substituents on their nitrogen atoms to act as NHC precursors for in situ catalytic applications was probed in ruthenium-promoted ring-opening metathesis and atom transfer radical polymerizations. Results obtained with 1:2 mixtures of [RuCl2(p-cymene)]2 and NHC•CO2 adducts were in line with those reported previously starting from preformed [RuCl2(p-cymene)(NHC)] complexes, whereas the NHC•CS2 zwitterions were almost completely inactive. To account for this dichotomy, the preparation of preformed ruthenium‚àíarene complexes from [RuCl2(p-cymene)]2 and NHC•CX2 inner salts was thoroughly investigated. As expected, imidazolium-2-carboxylates lost their CO2 moiety and afforded [RuCl2(p-cymene)(NHC)] complexes in high yields, whereas the NHC•CS2 betaines retained their zwitterionic nature and led to cationic complexes of the [RuCl(p-cymene)(NHC•CS2)]PF6 type. These stable, 18-electron species are the first examples of well-defined transition-metal complexes bearing chelating NHC•CS2 ligands. They were characterized by various analytical techniques, and the molecular structure of [RuCl(p-cymene)(IMes•CS2)]PF6 was determined by X-ray diffraction analysis. [less ▲]

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See detailATRP of methyl methacrylate and styrene catalysed by homobimetallic ruthenium-vinylidene complexes
Bicchielli, Dario ULg; Borguet, Yannick ULg; Sauvage, Xavier ULg et al

in Polymer Preprints (2008)

Styrene and Me methacrylate were subjected to atom transfer radical polymn. using a homobimetallic ruthenium-vinylidene complex (p-cymene)RuCl2/(PCy3)(styrylidene)RuCl2 as catalyst and Et 2 ... [more ▼]

Styrene and Me methacrylate were subjected to atom transfer radical polymn. using a homobimetallic ruthenium-vinylidene complex (p-cymene)RuCl2/(PCy3)(styrylidene)RuCl2 as catalyst and Et 2-bromoisobutyrate (EBiB), 1-phenylethyl bromide, or CCl4 as initiators (in toluene). The polymns. proceeded in a controlled fashion and the polydispersities were quite narrow. Using (EBiB), an induction period was obsd. The polymn. of styrene ceased after 80% conversion because of the degrdn. of the complex into inactive species. With both monomers and CCl4 as initiator, the mol. wt. of the polymers was lower than the calcd. value, i.e., the initiation efficiency was >1. [less ▲]

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See detailFacile Microwave-Assisted Synthesis of Cyclic Amidinium Salts
Aidouni, Adila; Bendahou, Soufiane; Demonceau, Albert ULg et al

in Journal of Combinatorial Chemistry (2008), 10(6), 886-892

The cyclization of N,N '-dialkyl or diaryl ethane-1,2-diamines or propane-1,3-diamines with inorganic ammonium salts and orthoesters proceeds briskly under microwave irradiation to afford the ... [more ▼]

The cyclization of N,N '-dialkyl or diaryl ethane-1,2-diamines or propane-1,3-diamines with inorganic ammonium salts and orthoesters proceeds briskly under microwave irradiation to afford the corresponding imidazolinium or tetrahydropyrimidinium salts. The transformation is highly versatile and tolerates a wide range of substituents and counterions. It could be scaled from 1 to 50 mmol without any difficulty. Because the workup is equally rapid and straightforward, this experimental procedure provides fast and convenient access to an important class of heterocyclic compounds that have found numerous applications as N-heterocyclic carbene precursors, organocatalysts, and ionic liquids. [less ▲]

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See detailATRP of methyl methacrylate catalysed by novel homo- and heterobimetallic ruthenium complexes
Borguet, Yannick ULg; Delfosse, Sebastien; Sauvage, Xavier ULg et al

in Polymer Preprints (2008), 49(2), 24-25

The atom transfer radical polymn. of Me methacrylate was studied in the presence of 6 novel homo- and heterobimetallic Ru complexes: (p-cymene)RuCl2/(PCy3)(ethylene)RuCl2, (p-cymene)RuCl2/(1,3-Mes2-4,5-X2 ... [more ▼]

The atom transfer radical polymn. of Me methacrylate was studied in the presence of 6 novel homo- and heterobimetallic Ru complexes: (p-cymene)RuCl2/(PCy3)(ethylene)RuCl2, (p-cymene)RuCl2/(1,3-Mes2-4,5-X2-imidazolin-2-ylidene)(ethylene)RuCl2 (X = H or Cl, Mes = 2,4,6-trimethylphenyl), and (p-cymene)RuCl2/[(2-dicyclohexylphosphinoethyl)cyclopentadienyl](Cp)TiX2 (X = F, Cl, or OBz). Et 2-bromoisobutyrate was used as initiator in all expts. All catalysts showed high efficiency in controlled synthesis of poly(Me methacrylate). Using the ruthenium/titanocene dibenzoate complex, the polymn. stopped after a few hours of reaction, affording nevertheless a polymer with a decent polydispersity. [less ▲]

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See detailMicrowave-assisted synthesis of imidazolinium salts
Hans, Morgan; Demonceau, Albert ULg; Delaude, Lionel ULg

in Polymer Preprints (2008), 49(2), 942-943

Imidazolinium salts were prepd. via microwave-assisted cyclocondensation of ethanediamines with triethoxy alkanes or triethoxymethyl benzene. The synthesized imidazolinium salts may be used as NHC ... [more ▼]

Imidazolinium salts were prepd. via microwave-assisted cyclocondensation of ethanediamines with triethoxy alkanes or triethoxymethyl benzene. The synthesized imidazolinium salts may be used as NHC precursors or ionic liqs. [less ▲]

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See detailMicrowave-assisted synthesis of vinyl esters through ruthenium-catalyzed addition of carboxylic acids to alkynes
Nicks, Francois ULg; Libert, Lionel ULg; Delaude, Lionel ULg et al

in Polymer Preprints (2008), 49(2), 944-945

1-Hexen-2-yl 4-acetoxybenzoate was regioselectively prepd. via microwave-assisted ruthenium-catalyzed addn. of 4-acetoxybenzoic acid to 1-hexyne. Species of catalysts, reaction time and temp. play roles ... [more ▼]

1-Hexen-2-yl 4-acetoxybenzoate was regioselectively prepd. via microwave-assisted ruthenium-catalyzed addn. of 4-acetoxybenzoic acid to 1-hexyne. Species of catalysts, reaction time and temp. play roles in the reaction respect to yields and selectivity, therefore were examd. Microwave effect was obsd. and preferred to the generation of the Markovnikov-type product compared to traditional heating. [less ▲]

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See detailOlefin metathesis reactions state of the art and outlook
Demonceau, Albert ULg; Delaude, Lionel ULg

in Chimica Oggi = Chemistry Today (2007), 25(5, SEP-OCT), 65-68

Olefin metathesis is a metal-catalysed organic reaction, which involves the statistical redistribution of carbon-carbon double bonds. Since its discovery in the 1950's, this transformation has gained ... [more ▼]

Olefin metathesis is a metal-catalysed organic reaction, which involves the statistical redistribution of carbon-carbon double bonds. Since its discovery in the 1950's, this transformation has gained widespread use in research laboratories and industry for making products ranging, from drugs and polymers to enhanced fuels. Its advantages include the ability to build up complex structural scaffolds with remarkable atom economy. Major industrial processes usually rely on inexpensive, ill-defined, multicomponent catalytic systems, while research laboratory applications take advantage of well-defined metal alkylidene complexes of molybdenum and ruthenium that combine high activities and ease of set-up under reproducible conditions, albeit at the price of a higher cost. [less ▲]

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