18947-78-9Relevant articles and documents
Chemical transformations of cis-W(CO)4(C5H 5N)2 in the ring-opening metathesis polymerization of norbornene
Bencze,Biro,Szabo-Ravasz,Mihichuk
, p. 499 - 503 (2007/10/03)
The six-coordinate W0 complex cis-W(CO)4(C 5H5N)2 has been found to be active in the in situ formation of a carbene species from norbornene, which generates a typical ring-opening metathesis product (ROMP). A proposed mechanism of initiation suggests that the reaction involves a 2,3-hydrogen shift in the coordinated norbornene (η2 → η1). The initiating carbenoid group is identified from the products of the spontaneous carbene-CO coupling and Wittig reactions test. Formation of W(CO)3(η 6-C6H5CH3) when toluene is the solvent, followed by reaction with the carbene, is blamed for catalyst deactivation.
Cathodic behaviour of 1-cycloalken-1-yl phenyl sulfones. I. Competition among dimerization, cleavage, isomerization and oligomerization processes in aprotic media
Prigent, Sylvie,Cauliez, Pascal,Simonet, Jacques,Peters, Dennis G.
, p. 892 - 900 (2007/10/03)
1-Cycloalken-1-yl phenyl sulfones 1a and 1b have been studied electrochemically in aprotic media (N,N-dimethylformamide, dimethyl sulfoxide, or acetonitrile containing tetraalkylammonium salts) at a mercury electrode. Their behaviour has been compared with that of 2-norbornen-2-yl phenyl sulfone 1c. The expected cleavage reaction is accompanied by a concomitant isomerization process into allyl sulfones that is triggered by electrogenerated bases. A quantitative determination of the product distribution during controlled-potential electrolyses suggests the formation of dimers and oligomeric species, arising through a Michael addition of the sulfone anions to the activated double bond of these sulfones.
Photochemistry of alkyl halides. 12. Bromides vs Iodides
Kopp, Paul J.,Adkins, Rick L.
, p. 2709 - 2717 (2007/10/02)
Conditions have been developed for optimizing ionic photobehavior material balances from alkyl bromides. Hydroxide ion as an efficient for the byproduct HBr while giving minimal competing photoreduction via electron transfer to the alkyl bomide. The photobehavior of bromides 1, 11, 25, and 40 has examined and with that of the corresponding iodides 2, 12, 26, 41 under conditions. In each case, the bromide higher yields of products derived from out of cage radical intermidiates than the corresponding iodide. However, with the 2-norbornyl bromides 11 and iodides 12 showed that, of products not formed from the out of cage 2-norbornyl radical 13, the bromides 11 gave a higher percentage of products from the ionic intermediates 15 and 16 than did the iodides. Thus, electron transfer within the radical pair 14 is apparently more rapid for bromides than iodides, as expected on the of the relative electronegativities of bromine iodine. It is that the substantially higher yields of out of radical products from alkyl bromides may be due in to formation of the radical pair with greater excess energy, which results in more rapid escape from the cage. The epimeric 2-norbornyl bromides 11x and 11n underwent no detectable interconversion and afforded somewhat different product ratios. The more hindered epimer 11n underwent conversion to products at a slower than 11x. By contrast, 12x and 12n underwent substantial interconversion via out of transfer of an iodine atom from iodide 12 to radical 13. Epimerization was significantly attenuated in the more viscous solvent tert-butyl alcohol.
Mechanism of Initiation of the Ring-opening Polymerization and Addition Oligomerization of Norbornene Using Unicomponent Metathesis Catalysts
Laverty, D. Theodore,Rooney, John J.
, p. 869 - 878 (2007/10/02)
The identities and yields of the low-molecular-weight products formed during ring-opening polymerization of norbornene in benzene solvent using several unicomponent metal halide catalysts (W, Mo, Re, Ru, Os and Ir) were extensively investigated.Dimers and
