699-96-7Relevant academic research and scientific papers
Self-immobilizing precatalysts: Norbornene-bridged zirconium ansa-metallocenes
Polo, Eleonora,Forlini, Fabrizio,Bertolasi, Valerio,Boccia, Antonella Caterina,Sacchi, Maria Carmela
experimental part, p. 1544 - 1556 (2009/07/30)
We report here the synthesis of new tethered biscyclopentadienyl and bisindenyl zirconocenes, bearing one unsaturation on the interannular bridge, and their use as self-immobilizing catalysts. They proved to be active catalysts towards ethylene polymerization in solution, with activities comparable to those displayed by commercial rac-Et-(Ind)2ZrCl2. When tested as self-polymerization catalysts under suitable experimental conditions, they gave colored precipitates that, once reactivated with MAO, were significantly active in ethylene polymerization, although lower than those of the corresponding catalytic systems in solution. The molecular weights of the produced polymers were similar to those obtained with the same catalysts in solution, but their distribution resulted to be broader, with values typical of heterogeneous catalytic systems. From 13C NMR studies we had the first spectroscopic evidence of the actual incorporation of a metallocene of this type into a polymeric chain.
Synthesis of novel carbocyclic nucleosides and pro-tides derived from 4-oxatricyclo[4.2.1.03,7]nonane-9-methanol
Hrebabecky, Hubert,Dracinsky, Martin,Holy, Antonin
, p. 1331 - 1349 (2008/09/17)
(1R*,2R*,3R*,6R*,7S*)-2-Amino-4- oxatricyclo[4.2.1.03,7]nonane-9-methanol (9) was prepared from (1R*,2R*,3R*,4S*)-bicyclo[2.2.1]hept-5-ene-2, 3-dimethanol by treatment with benzyl azidoformate followed by hydrogenolysis. The amine 9 was transformed to thymine and purine nucleoside analogues. The prepared analogues were converted to corresponding Pro-Tides by treatment with methyl N-[chloro(phenoxy)phosphoryl]-L-alaninate in the presence of 1-methylimidazole or tert-butylmagnesium chloride.
Cyclopentanedi- and tricarboxylic acids as squalene synthase inhibitors: Syntheses and evaluation
Shen, Wang,Garvey, David S.,Cohen, Jerry,Stein, Herman,Rosenberg, Saul H.
, p. 891 - 896 (2007/10/03)
Based on earlier lead squalene synthase inhibitor A-87049 (3) and zaragozic acids, a series of cyclopentanedi- and tricarboxylic acids were synthesized and evaluated against the enzyme. Some exhibited good potency and SAR revealed the importance of conformation and substitution pattern of these synthetic inhibitors.
A Synthetic Strategy for the Construction of a Novel Series of Rigid Supramolecular Triads
Lawson, James M.,Paddon-Row, Michael N.
, p. 1641 - 1643 (2007/10/02)
A method is described for constructing totally rigid triad (trichromophoric) supramolecular systems, D2-B1-D1-B2-A, in which the chromophores D2 (dimethylaniline), D1 (dimethoxynaphthalene), and A (dicyanovinyl) are fused to bridges, B1 and B2, consisting of linearly fused norbornyl and bicyclohexanyl units.
Enzymatic resolution of norbor(NE)nylmethanols in organic media and an application to the synthesis of (+)- and (-)-endo-norbornene lactone
Janssen,Klunder,Zwanenburg
, p. 5513 - 5538 (2007/10/02)
The enzymatic resolution of some norbornene carboxylic acids, norbornenylmethanols and -methylamines was evaluated. The kinetic resolution of norbornyl- and norbornenylmethanols by Porcine Pancreatic Lipase (PPL)-catalyzed transesterification in methyl acetate as the solvent leads to corresponding acetates and remaining methanols both of high enantiomeric purity. A useful application is the synthesis of both enantiomers of endo-norbornene lactone 8n via transesterification of iodolactone 18. The influence of structural variations on the efficiency of the PPL-catalyzed resolution of lactone methanols 21, 23, 25 and 28, at the optimal reaction conditions established for iodolactone 18, was investigated.
A Convenient Synthesis of Both Enantiomeric 2,3-Disubstituted 5-Norbornenes from D-Mannitol
Takano, Seiichi,Kurotaki, Ayako,Ogasawara, Kunio
, p. 1075 - 1078 (2007/10/02)
A convenient synthesis of both enantiomeric trans- and cis-2,3-disubstituted 5-norbornenes (bicycloheptenes), 2 and 3, has been developed by utilizing the Diels-Alder reaction between cyclopentadiene and chiral dienophiles obtained from a single chiral template D-mannitol (1).
Platinum Chloride-Diphosphine-Tin(II) Halide Systems as Active and Selective Hydroformylation Catalysts
Hayashi, Teruyuki,Kawabata, Yasuziro,Isoyama, Toyoshiro,Ogata, Ikuei
, p. 3438 - 3446 (2007/10/02)
The hydroformylation of 1-alkenes was efficiently catalyzed by PtCl2-diphosphine-SnX2 systems whose diphosphines were 1,4-bis(diphenylphosphino)butane derivatives with rigid ring skeletons.The effects of the structure of diphosphines, the P/Pt atomic ratio, the sort of tin(II) halide or solvent, the reaction variables, and the structure of olefins on the relative rate and the product distribution were investigated.A higher reaction rate than when using HRh(CO)(PPh3)3, and a linearity of aldehydes up to 99percent, were attained.The coordination structure of the effective diphosphines as well as the reasons for the rate enhancement and for the excellent selectivity were discussed.
Thallium in Organic Synthesis. 56. A Novel Oxidative Intramolecular Cyclization/Rearrangement of 5-Norbornene-trans-2,3-dicarboxylic Acid with Thallium(III) Trifluoracetate (TTFA)
Taylor, Edward C.,Jagdmann, G.Erik,McKillop, Alexander
, p. 3373 - 3375 (2007/10/02)
Treatment of 5-norbornene-trans-2,3-dicarboxylic acid (5) with thallium(III) trifluoracetate (TTFA) and BF3*Et2O results in oxidative intramolecular cyclization, accompanied by rearrangement, to give the previously unknown 5,7-dihydroxy-2,3-norbornanedicarboxylic acid di-γ-lactone (9).
