Showing papers on "Metathesis published in 1994"
TL;DR: In this paper, the ruthenium catalyst exhibited metathesis activity for a range of substrates, including alkyls, alkarnes, Ph, CO2Me, SnBu3, TMS, Cl, Br, I.
Abstract: Ruthenium carbene 1 (Cl2(PCy3)2RuCHCHCPh2) mediates the efficient and selective conversion of acyclic dienynes to fused bicyclic [n.m.0] rings containing five-, six-, and seven-membered rings. Studies with various X-substituted acetylenes (X = H, alkyls, Ph, CO2Me, SnBu3, TMS, Cl, Br, I) suggest that the dienyne metathesis is sensitive not only to these substituents but also to the catalysts employed. Among the various metal alkylidenes examined, only the ruthenium catalyst 1 exhibited metathesis activity for a range of substrates. These observations further expand the scope of catalytic RCM for the construction of complex organic compounds.
210 citations
TL;DR: An efficient method for the construction of five and six-membered cyclic vinyl ethers from unsaturated esters using stoichiometric titanium reagents to convert the esters to acyclic olefinic enol ethers which are then transformed to the desired products by catalytic ring-closing Olefin metathesis with a molybdenum alkylidene complex is described in this article.
Abstract: An efficient method for the construction of five- and six-membered cyclic vinyl ethers from unsaturated esters using stoichiometric titanium reagents to convert the esters to acyclic olefinic enol ethers which are then transformed to the desired products by catalytic ring-closing olefin metathesis with a molybdenum alkylidene complex is described
187 citations
110 citations
91 citations
TL;DR: In this paper, the synthesis of the ABCD ring system of manzamine A has been achieved using the olefin metathesis cyclization reaction for the crucial macrocyclic ring D formation step.
89 citations
TL;DR: In this paper, the authors proposed a new catalyst system for self-metathesis of unsaturated fatty acid esters, which can be used as intermediate for the production of polymers and other useful chemical products such as civetone.
77 citations
64 citations
TL;DR: In this paper, the molybdenum alkylidene-catalyzed metathesis of α,ω-dienes containing a nitrogen atom in the chain linking the two olefinic functional groups was developed.
64 citations
54 citations
TL;DR: Poly(disilanyleneethynylene)s are obtained by ring opening metathesis polymerization of tetrasilacycloocta-3-7-diynes catalyzed by high valent Schrock carbyne complexes of the type (RO) 3 W≡CR' (RO= Me 3 CO, CF 3 Me 2 CO; R'= Me, Et) as mentioned in this paper.
Abstract: Poly(disilanyleneethynylene)s [Si(R) 2 Si(R) 2 -C≡C-Si(R') 2 Si(R') 2 -C≡C] n (R=, R'= Me, Et) are obtained by ring opening metathesis polymerization of tetrasilacycloocta-3-7-diynes catalyzed by high valent Schrock carbyne complexes of the type (RO) 3 W≡CR' (RO= Me 3 CO, CF 3 Me 2 CO; R'= Me, Et)
47 citations
TL;DR: In this paper, a low-loading metathesis catalysts were presented in which rhenium is directed to favorable sites on the surface of γ-alumina.
TL;DR: The four-coordinate bis(imido) dialkyl complex [Mo(N-2,6-Pri2C6H3)(N-But)(CH2CMe3)2] is readily converted to well-defined alkylidene metathesis catalysts upon treatment with alcoholic or phenolic activators.
Abstract: The four-coordinate bis(imido) dialkyl complex [Mo(N-2,6-Pri2C6H3)(N-But)(CH2CMe3)2] is readily converted to well-defined alkylidene metathesis catalysts upon treatment with alcoholic or phenolic activators.
TL;DR: In this paper, 1-(1-alkynyl)-4-methoxy-4-methyl-5-alkylidenecyclopentenones were transformed with high stereoselectivity into 4-mETHoxy, 4-methyl, and 5-methyl cyclobutenediones.
Abstract: 1-(1-Alkynyl)-4-methoxy-4-methyl-2-cyclobutenols, prepared by nucleophilic functionalization of cyclobutenediones, were transformed with high stereoselectivity into 4-methoxy-4-methyl-5-alkylidenecyclopentenones. The action of stoichiometric Hg(OCOCF 3 ) 2 and then metathesis with NaCl produced 5-(1-(chloromercurio)alkylidene)-4-methoxy-4-methyl-2-cyclopentenones which were stereospecifically functionalized by palladium-mediated allylation and hydroxybutenylation. Treatment with Br 2 /DMSO led to stereospecific bromodemercuration. The 1-(1-alkynyl)-4-methoxy-4-methyl-2-cyclobutenols underwent efficient and very stereoselective tandem ring expansion-functionalizations in the presence of three different allylic chlorides and a catalyst system composed of 10% Hg(OCOCF 3 ) 2 and 10% PdCl 2 . All products can be obtained with a stereoselectivity greater than 99:1 at the exocyclic alkene
TL;DR: In this article, the reaction between [Ir(coe)_2Cl]_2(coe = cyclooctene) and AgO_2CCF_3(4 equiv.) produces a highly active system for metathesis/isomerization of acyclic olefins, including methyl oleate.
Abstract: Reaction between [Ir(coe)_2Cl]_2(coe = cyclooctene) and AgO_2CCF_3(4 equiv.) produces a highly active system for metathesis/isomerization of acyclic olefins, including methyl oleate.
TL;DR: In this article, homochiral norbornene monomers derived from amino acids undergo ring-opening metathesis polymerisation with [Mo(CHCMe2Ph)(NC6H3Pri2-2,6)(OBut)2] to give narrow molecular mass distributions.
Abstract: Homochiral norbornene monomers derived from amino acids undergo ring-opening metathesis polymerisation with [Mo(CHCMe2Ph)(NC6H3Pri2-2,6)(OBut)2] to give homochiral polymers with narrow molecular mass distributions.
TL;DR: In this paper, the reactivity of two alkylidynetungsten complexes, [W(CCMe3)(CH2CMe3)3] and [W (CCMe 3)Cl3(dme)] (dme = 1,2-dimethoxyethane), was determined with the surface of different inorganic oxides, such as silica, alumina, silica-alumina and niobia; their catalytic activity was tested for the metathesis of cis-pent-2-ene.
Abstract: The reactivity of the two alkylidynetungsten complexes, [W(CCMe3)(CH2CMe3)3] and [W(CCMe3)Cl3(dme)](dme = 1,2-dimethoxyethane), was determined with the surface of different inorganic oxides, such as silica, alumina, silica-alumina and niobia; their catalytic activity was tested for the metathesis of cis-pent-2-ene. The most efficient solids resulted from the interaction of these complexes with the surface of partially dehydroxylated niobia and silica–alumina. An attempt to identify the surface complexes on niobia (most active system) and silica (less active system) revealed the presence of a number of different anchored complexes, some of them bearing a neopentylidene ligand. The possible correlation between catalytic activity and some of the most probable surface entities is discussed.
TL;DR: In this article, a number of 7-oxanorbornene derivatives with hydroxymethyl, methoxymethyl and acetoxylic acid functionalities were synthesised and investigated as monomers in ring-opening metathesis polymerisation (ROMP) catalysed by commercial ruthenium trichloride in aqueous ethanolic solvents.
Abstract: A number of 7-oxanorbornene derivatives with hydroxymethyl, methoxymethyl and acetoxymethyl functionalities were synthesised and investigated as monomers in ring-opening metathesis polymerisation (ROMP) catalysed by commercial ruthenium trichloride in aqueous ethanolic solvents. Comparison was made with related polymerisations of 7-oxanorbornene derivatives with anhydride, methoxymethyl and carboxylic acid functionalities. The structures of the polymers were investigated by 1H and 13C NMR and their molar masses and molar mass distributions by gel-permeation chromatography.
TL;DR: A soluble liquid crystalline conducting polymer was obtained by metathesis cyclopolymerization of the compound (CH 2 C≡CH) 2 NCO(CH 2 ) 10 OPhPhCN.
Abstract: A soluble liquid crystalline conducting polymer was obtained by metathesis cyclopolymerization of the compound (CH 2 C≡CH) 2 NCO(CH 2 ) 10 OPhPhCN
TL;DR: In this paper, a self metathesis of vinyltrimethylsilane in the presence of an oxygenated benzene solution of RuCl 2 (PPh3)3 and RuCl2(PPh4)4 follows an unusual course and yields two products, 1,2-bis(silyl)ethene (E) and 1,1-bis (sily l)ethenes, with products of dimerization, namely 1,4-bis-silylsbutenes-2 (E + Z) and butenylsilanes as
TL;DR: Methyl-terminated polyenes containing up to 20 double bonds are synthesized by metathesis polymerization of conjugated acyclic diene or trienes.
Abstract: Methyl-terminated polyenes containing up to 20 double bonds are synthesized by metathesis polymerization of conjugated acyclic diene or trienes. The reactions are clean and high yields are obtained
TL;DR: In this article, four and six-coordinate mixed-imido complexes of molybdenum were described and the structures of [Mo(Nad)(NC6F5)Cl2(dme)](ad = adamantyl) and [Mo[Nad]-NC 6F5)(CH2CMe2Ph)2] are reported.
Abstract: Novel four- and six-coordinate mixed-imido complexes of molybdenum are described and the structures of [Mo(Nad)(NC6F5)Cl2(dme)](ad = adamantyl) and [Mo(Nad)(NC6F5)(CH2CMe2Ph)2] are reported.
TL;DR: In this paper, the metathesis of vinyltrimethylsilane is efficiently catalysed by many ruthenium complexes yielding E -bis(silyl)ethene and, unexpectedly, 1,1-bis(Silyl)-ethene as main products accompanied by products of dimerization and co-dimerization.
TL;DR: In this article, the synthesis of N-phenylnorbornene-5,6-dicarboximides (NDIs) with substituents at different positions in the aromatic ring and their polymerization by ring-opening metathesis polymerization (ROMP) leading to high-temperature polymers are described.
Abstract: The synthesis of N-phenylnorbornene-5,6-dicarboximides (NDIs) with substituents at different positions in the aromatic ring and their polymerization by ring-opening metathesis polymerization (ROMP) leading to high-temperature polymers are described. A structure-property relationship study showed that the polymer properties are significantly influenced by the size and position of the substituent groups on the ring. Substitution at the ortho position leads to an increase in the T g of the polymer, whereas metsubstitution has the opposite effect. An increase in the size of the substituent for ortho-substituted polymers is found to further increase the T g
TL;DR: In this article, Tungsten aryloxo-complexes (1 and 2 ) were found to be superior catalysts for the unsaturated alcohols process, bearing different protecting groups at glucose units.
TL;DR: MoCl5-based catalysts were more effective for the polymerization of these monomers than WCl6-based catalyst systems as mentioned in this paper, and these polymers exhibited good solubility in common organic solvents and could be easily cast on glass plates to give thin films.
Abstract: Poly(triethyldipropargylphosphonoacetate) (TDPA), poly[(tetraethyl dipropargylmethylenediphosphonate) (TDMDP) were prepared by metathesis polymerization using transition-metal catalysts. MoCl5-based catalyst systems were more effective for the polymerization of these monomers than WCl6-based catalyst systems. Resulting polymers exhibited good solubility in common organic solvents and could be easily cast on glass plates to give thin films. Third-harmonic Maker fringe technique was used to measure third-order nonlinear susceptibility,x(3), for thin film of poly(TDPA). Thex(3) was evaluated to be 3.4x10-11 esu at incident wavelength of 1.907μm.
TL;DR: In this paper, it was shown that the deactivation is due to the isomerization of the Mo-cyclobutane intermediate into π-complexes of the alkenes with the Mo4+ ions.
TL;DR: In this article, the σ-bond metathesis products of [{Ln(C5Me5)2H}2] and [W(c5H5)5] were shown to afford σbond products with the weaker W-H bond, via dehydrocoupling between the Ln−H bond and the C−H (but not weaker W−H) bond.
Abstract: Reactions of [{Ln(C5Me5)2H}2](Ln = Y, Sm) with [W(C5H5)2H2] afford the σ-bond metathesis products [(C5Me5)2Ln(µ-η1, η5-C5H4)(µ-H)2W(C5H5)], via dehydrocoupling between the Ln–H bond and the C–H (but not the weaker W–H) bond of [W(C5H5)2H2].