- Electron Transfer Rate Determinations: Facile Electron Transfer from 1,1,2,2-Tetrakis(4-methoxyphenyl)ethanediol
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The oxidation reactions of 1,1,2,2-tetrakis(4-methoxyphenyl)ethanediol, 1, by 2,3-dichloro-5,6-dicyanobenzoquinone (DDQ) and Fe(III) complexes have been found to proceed cleanly in the presence of an appropriate base to give 4,4'-dimethoxybenzophenone.The rates of oxidation of 1,1,2,2-tetrakis(4-methoxyphenyl)ethanediol by 2,3-dichloro-5,6-dicyanobenzoquinone and Fe(III)(4-methoxy-2,2'-bipyridyl)3(ClO4)3 have been measured.Evaluation of the rate constants has allowed calculation of E0(excit.) for 1.Compared to 4-methoxytoluene, 1 is much easier to oxidize, following the general trend that phenyl-phenyl interactions lower the oxidation potentials of tetraarylethanediols relative to their corresponding monoaryl model compounds.
- Penn, John H.,Duncan, Joseph H.
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- Acid catalysis vs. electron-transfer catalysis via organic cations or cation-radicals as the reactive intermediate. Are these distinctive mechanisms?
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Proton transfer to aromatic and olefinic donors (D) leads 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 separate electrophilic and homolytic processes, and rigorous experimental evidence is required to establish whether acid catalysis and electron-transfer catalysis actually represent distinct mechanistic categories. Acta Chemica Scandinavica 1998.
- Rathore, Rajendra,Kochi, Jay K.
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p. 114 - 130
(2007/10/03)
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- RADICAL CATION CATALYZED PINACOL-PINACOLONE REARRANGEMENT
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When electron-rich benzopinacols are electrooxidized or treated with catalytic amounts of NOBF4 the corresponding pinacolones are obtained in quantitative yields.Control experiments rule out the possibility of adventitious acid intervening in the reaction
- Saniba J. Arce de,Carrion, Arturo E.
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p. 7837 - 7840
(2007/10/02)
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- Novel reductive couplinog-rearrangement of carbonyl compounds with metal/Lewis acid under irradiation of ultrasonic wave
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Novel reductive coupling-rearrangement of carbonyl compounds such as benzophenones with Al or Zn/ AlCl3 in CH3CN under irradiation of ultrasonic wave gave benzopinacolones via epoxides in good yields.
- Sato, Ryu,Nagaoka, Takeshi,Saito, Minoru
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p. 4165 - 4168
(2007/10/02)
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