Search results for "Norbornene"
showing 10 items of 40 documents
Ethene/norbornene copolymerization with (isodicyclopentadienyl)titanium complex-MAO catalyst
2007
Norbornene (NB) homopolymerization and ethene/NB copolymerizations with a silylene-bridged (isodicyclopentadienyl)(tert-butylamido)titanium dichloride-methylalumoxane (MAO) catalyst system were investigated. This catalytic system shows no efficiency towards NB homopolymerization but produces poly(ethene-co-norbornene)s. An increase in the initial NB feed content leads to a loss of copolymerization activity as well as NB copolymer incorporation. The structure of the isodicyclopentadienyl fragment (IsodiCp) has a strong limiting effect on comonomer incorporation possibilities.
Synthesis and structure of stable cis-dimethyl complex of oxotungsten(VI)
2007
Abstract Oxotungsten(VI) complex cis -[WO(L t Bu )Me 2 ] (L t Bu = methylamino- N , N -bis(2-methylene-4-methyl-6- tert -butylphenolate) dianion) was prepared by the transmetallation reaction of [WO(L t Bu )Cl 2 ] (either cis or trans isomer) with methyl magnesium iodide. This unexpectedly stable dialkyl complex can be activated by Et 2 AlCl to catalyze the ring-opening metathesis polymerization of norbornene.
Dioxomolybdenum(VI) complexes with tri- and tetradentate aminobis(phenolate)s
2005
Abstract The reactions of tridentate ligands, bis(2-hydroxy-3,5-dimethylbenzyl)methylamine (H2ONOMe) and bis(2-hydroxy-3-tert-butyl-5-methylbenzyl)methylamine (H2ONOtBu) with [MoO2(acac)2] (1) in methanol lead to the precipitation of monomeric dioxomolybdenum(VI) complexes [MoO2(ONOMe)(MeOH)] · MeOH (2a) and [MoO2(ONOtBu)(MeOH)] · MeOH (2b), respectively. Identical reactions in acetonitrile provide dimeric complexes [Mo2O2(μ-O)2(ONOMe)2] (3a) and [Mo2O2(μ-O)2(ONOtBu)2] (3b). The reactions of 1 with tetradentate ligands, N,N′-bis(2-hydroxy-3,5-dimethylbenzyl)-N,N′-dimethylethane-1,2-diamine (H2ONNOMe) and N,N′-bis(2-hydroxy-3,5-di-tert-butylbenzyl)-N,N′-dimethylethane-1,2-diamine (H2ONNOtBu)…
Pauson-Khand reaction of internal dissymmetric trifluoromethyl alkynes. Influence of the alkene on the regioselectivity.
2014
Abstract: The scope of the Pauson-Khand reaction (PKR) of internal trifluoromethyl alkynes, previously described with norbornadiene, is expanded to norbornene and ethylene. A thorough structural analysis of the resulting PK adducts has been carried out to unveil that α-trifluoromethylcyclopentenones are preferred in all cases, independently of the electronic properties of the alkyne. The regioselectivity observed with norbornadiene and ethylene is higher than in the case of norbornene.
Metabolism of polychlorinated norbornenes by Clostridium butyricum.
1972
STUDIES of the metabolism of cyclodien-insecticides, such as dieldrin, endrin, endosulphan, have revealed valuable information about their fate in the ecosystem1. With all metabolites identified so far, however, the hexachlorinated norbornene moiety remains unchanged2,3. Only from photodieldrin, a cage-like derivative of dieldrin, have dechlorinated metabolites been reported4,5.
Assessment of Catalysis by Arene‐Ruthenium Complexes Containing Phosphane or NHC Groups bearing Pendant Conjugated Diene Systems
2015
Two p-cymene-ruthenium complexes 1 and 2 were isolated in high yields by treating the [RuCl2(p-cymene)]2 dimer with new hybrid phosphane- or NHC-linked diene ligands. Both complexes were fully characterized by NMR spectroscopy, and the molecular structure of the ruthenium–p-cymene complex 1, containing the phosphane–diene ligand system, was determined by X-ray diffraction analysis. The catalytic activities of both compounds were probed in atom-transfer radical addition (ATRA) and polymerization (ATRP), in the cyclopropanation of olefins, in the ring-opening metathesis polymerization (ROMP) of norbornene, and in the synthesis of enol esters from hex-1-yne and 4-acetoxybenzoic acid.
Copolymerization of ethylene with norbornene or 1-octene using supported ionic liquid systems
2016
Copolymerization of ethylene with norbornene (E/NB) and ethylene with 1-octene (E/Oct) is performed using supported ionic liquid (SIL) systems, in which metallocene (Cp2VCl2) or post-metallocene [VCl2(salenCl2)] vanadium catalysts are immobilized in pyridinium chloroaluminate ionic liquid supported on silica. The studied SIL catalysts show higher activities as well as stability than their non-supported analogues. In addition, higher activities and better comonomer incorporation are observed for norbornene (above 30 mol%). The comonomer incorporation has considerable influence on copolymer molecular weight (M w), melting temperature, crystallinity degree, and microstructure of the copolymers…
Titanium and vanadium catalysts with oxazoline ligands for ethylene-norbornene (co)polymerization
2018
A series of catalysts, (Py-ox)TiCl4, (Py-box)TiCl4, (Py-ox)VCl3, (Py-box)VCl3, SIL/(Py-ox)VCl3, SIL/(Py-box)VCl3, with 2-(1,3-oxazolin-2-yl)pyridine (Py-ox) and 2,6-bis(1,3-oxazolin-2-yl)pyridine (Py-box) ligands, silica support modified by 1-[3-(triethoxysilyl)propyl]pyridinium ethylchloroaluminate ionic liquid (SIL), activated by AlEt2Cl, AlEtCl2, and methylaluminoxane (MMAO) were studied in ethylene polymerization and ethylene-norbornene copolymerization. Single-crystal X-ray diffraction is given for both Py-ox and Py-box. The complexation was confirmed by NMR and ESI-MS methods. All complexes were found to be active in ethylene polymerization with better performance of the vanadium cata…
Experimental and Theoretical Electron Density Determination for Two Norbornene Derivatives: Topological Analysis Provides Insights on Reactivity
2016
The electron density distribution of two substituted norbornene derivatives (cis-5-norbornene-endo-2,3-dicarboxylic anhydride (1) and 7-oxabicylo[2.2.1]hept-5-ene-exo-2,3-dicarboxylic anhydride (2) has been determined from low-temperature (20 K) X-ray diffraction data and from DFT calculations with periodic boundary conditions. Topological analysis of the electron density is discussed with respect to exo-selective additions, the partial retro-Diels-Alder (rDA) character of the ground state, and intermolecular interaction energies.
A Domino Ring‐Closure Followed by Retro‐Diels–Alder Reaction for the Preparation of Pyrimido[2,1‐ a ]isoindole Enantiomers
2016
A simple method was developed to prepare pyrimido[2,1-a]isoindole derivatives by using di-endo- and di-exo-ethyl 3-aminobicyclo[2.2.1]hept-5-ene-2-carboxylate enantiomers as chiral sources. The method is based on a domino ring-closure reaction of norbornene 2-aminohydroxamic acid followed by microwave-induced retro-Diels–Alder reaction. In the case of enantiomeric starting substances, the chirality is transferred from norbornene derivatives to pyrimido[2,1-a]isoindoles. The configurations of the synthesized compounds were determined by 1D and 2D NMR spectroscopy [based on 2D NOE cross-peaks and 3JH,H coupling constants] and X-ray crystallography.