Norbornene

About: Norbornene is a research topic. Over the lifetime, 5628 publications have been published within this topic receiving 104495 citations. The topic is also known as: norbornylene & norcamphene.

Novel Ruthenium-Based Catalyst Systems for the Ring-Opening Metathesis Polymerization of Low-Strain Cyclic Olefins

Abstract: Highly active catalyst systems for the ring-opening metathesis polymerization (ROMP) of strained (norbornene) and low-strain (cyclooctene) olefins are readily prepared from RuCl2(arene)(PR3) precursors (directly available by addition of a phosphine to the stable [(arene)RuCl2]2 dimers) after activation with (trimethylsilyl)diazomethane. Durene or p-cymene as arene ligands, together with a sterically demanding basic phosphine (typically tricyclohexylphosphine), promoted the formation of the most active polymerization catalysts. The effects of arene and phosphine ligands and of the solvent on polynorbornene and polyoctenamer molecular weight distributions and microstructures were investigated. The excellent functional group compatibility of the catalyst system was illustrated by the synthesis of a variety of polyoctenamers bearing epoxide, acid, ether, ester, acetal, and bromine functionalities. The polymers were isolated in quite good yields. The striking positional influence of the functional group on the...

Addition of Olefins to Aromatic Ketones Catalyzed by Rh(I) Olefin Complexes

Abstract: The rhodium bis-olefin complex [C5Me5Rh(C2H3SiMe3)2], 1, has been shown to be a catalyst for the selective addition of olefins to the ortho position of aromatic ketones. The addition of vinyltrimethylsilane to benzophenone was studied by NMR spectroscopy, which indicated that 1 was the catalyst resting state for this process. This reaction was applied to a series of olefins (allyltrimethylsilane, 1-pentene, norbornene, 2,2‘-dimethyl-3-butene, cyclopentene, and vinyl ethyl ether) and aromatic ketones (benzophenone, 4,4‘-dimethoxybenzophenone, 3,3‘-bis(trifluoromethyl)benzophenone, dibenzosuberone, acetophenone, p-chloroacetophenone, and p-(trifluoromethyl)acetophenone). The dependence of the turnover frequency on substrate concentration was investigated. In the presence of excess ketone the formation of a benzophenone complex, 5, [(C5Me5Rh)2-η4-η4-C6H5C(O)Ph] was observed after consumption of olefin. Active catalyst is regenerated upon addition of olefin to 5. On the basis of kinetic experiments and labeli...

High-yield epoxidations with hydrogen peroxide and tert-butyl hydroperoxide catalyzed by iron(III) porphyrins: heterolytic cleavage of hydroperoxides

Abstract: The reactions of hydrogen peroxide or tert-butyl hydroperoxide with cyclooctene and norbornene, catalyzed by iron(III) tetrakis(pentafluorophenyl)porphyrin chloride and other electronegatively-substituted porphyrins, produced 60-100% epoxide yields. The epoxynorbornane yield has the same ratio of exo/endo isomers as is obtained using pentafluoroiodosylbenzene, an oxidant which produces the iron(IV) radical cation (oxene) intermediate. These results demonstrate heterolytic cleavage of these peroxides in the catalyzed reaction

Ethylene/Norbornene Copolymerizations with Titanium CpA Catalysts

Abstract: Group 4 ansa-cyclopentadienylamido (CpA) complexes [Me2Si(Cp‘)(NR)]MCl2 (R = alkyl, M = Ti, Zr) efficiently copolymerize ethylene with a variety of α-olefins. Ethylene/norbornene copolymerization reactivity ratios were determined at 40 °C for CpA catalysts [Me2Si(Cp‘)(NtBu)]TiCl2 (Cp‘ = Me4Cp, 2,4-Me2Cp, 3-tBuCp, Ind), and the resulting values are low (r1 = 2.0−5.1, r2 → 0), suggesting a tendency toward alternating comonomer insertion at high norbornene/ethylene feed ratios. As reaction temperature is increased and norbornene concentration is decreased, productivity increases and norbornene incorporation decreases. No more than 46 mol % norbornene is incorporated into the copolymer using these CpA catalysts even at low feed ratios (E/N ≥ 0.02), and norbornene homopolymerizations with [Me2Si(Me4Cp)(NtBu)]TiCl2 proceed to very low conversion (<1%). 13C NMR spectroscopy of CpA-derived poly(ethylene-co-norbornene)s shows the copolymers contain virtually no consecutive norbornene sequences, and the microstruct...