Catalytic Epoxidation of Hindered Olefins with Dioxygen. Fast Oxygen Atom Transfer to Olefin Cation Radicals from Nitrogen Oxides
作者:Eric Bosch、Jay K. Kochi
DOI:10.1021/ja953786n
日期:1996.1.1
efficiently converted to epoxides by dioxygen at 25 °C in dichloromethane containing catalytic amounts of nitrogen oxides (NO2, NO+, NO, etc.). Nitrogen dioxide also effects the direct (stoichiometric) epoxidation of the same hindered olefins. Olefin cation radicals are spectrally identified as the first observable intermediate, and separate experiments confirm the facile transfer of an oxygen atom from nitrogen
Addition of trifluoroacetic acid to adamantylideneadamantane in dichloromethane solution under oxygen in the dark results in a rapid oxygenation of the olefin. The reaction is proposed to proceed through a mechanism involving proton-induced electron transfer from the olefin to oxygen giving its radicalcation and a hydroperoxy radical followed by their subsequent reactions.
Electron-transfer reactions of hindered olefins induced by aminium salts.
作者:Luigi Lopez、Luigino Troisi、Giuseppe Mele
DOI:10.1016/s0040-4039(00)71233-0
日期:1991.1
Hinderedolefins 1–6, by reaction with aminium salts, can afford, in relations to the reaction conditions and the peculiar features of the reagents, different reaction products such as dioxetanes, epoxides, ketones, or homoallylic, allylic and vinylic halogenated derivatives.
Acid Catalysis vs. Electron-Transfer Catalysis via Organic Cations or Cation-Radicals as the Reactive Intermediate. Are These Distinctive Mechanisms?
作者:Rajendra Rathore、Jay K. Kochi、Augusto Canavesi、Larry L. Miller、Giovanni V. Sebastiani、George W. Francis、József Szúnyog、Bengt Långström
DOI:10.3891/acta.chem.scand.52-0114
日期:——
Proton transfer to aromatic and olefinic donors (D) lends to the facile interchange of transient carbocations (DH+) and cation-radical (D+.). The same types of cation and cation-radical are reactive intermediates in the acid catalysis and the electron-transfer catalysis of such organic transformations as benzylic coupling, epoxide.-pinacol rearrangements and cis-trans isomerization of stilbenes when they are both carried out under otherwise identical reaction conditions, However, the rapid exchange of diamagnetic cations and paramagnetic cation-radicals blurs the traditional view of sepal ate electrophilic and homolytic processes, and rigorous experimental evidence is required to establish whether acid catalysis and electron-transfer catalysis actually represent distinct mechanistic categories.