EPR Support for the Ketyl Radical-Anion “Triggered” [3,3]-Sigmatropic Rearrangement

2002 ◽  
Vol 67 (18) ◽  
pp. 6579-6581 ◽  
Author(s):  
Eric J. Enholm ◽  
Merle A. Battiste ◽  
Maria Gallagher ◽  
Kelley M. Moran ◽  
Angelo Alberti ◽  
...  
Keyword(s):  
Radical Anion ◽  
Sigmatropic Rearrangement ◽  
Ketyl Radical

Hammett-Streitwieser Reaction Constants for the Electroreduction of Diaryl Ketones in Aprotic Media

1996 ◽  
Vol 49 (8) ◽  
pp. 901 ◽  
Author(s):  
E Wagnerczauderna ◽  
MK Kalinowski
Keyword(s):  
Cyclic Voltammetry ◽  
Dimethyl Sulfoxide ◽  
Propylene Carbonate ◽  
Radical Anion ◽  
Electrode Reaction ◽  
Hexamethylphosphoric Triamide ◽  
Ketyl Radical ◽  
Donor Numbers ◽  
Reaction Constants ◽  
Solvent Acidity

Cyclic voltammetry has been used to measure formal potentials of seven aromatic ketone/ketyl radical anion systems in benzonitrile, acetonitrile , propylene carbonate, acetone, N,N- dimethylformamide, N-methylpyrrolidin-2-one, dimethyl sulfoxide and hexamethylphosphoric triamide. The values measured in each solvent obey the Hammett- Streitwieser equation; the reaction constants were found to depend on the solvent acidity and basicity expressed by acceptor and donor numbers, respectively. The results are discussed in terms of the solvation of the products and reactants of the electrode reaction.

Mechanism of the Electrochemical Carboxylation of Aromatic Ketones in Dimethylformamide

2003 ◽  
Vol 68 (8) ◽  
pp. 1379-1394 ◽  
Author(s):  
Abdirisak A. Isse ◽  
Armando Gennaro
Keyword(s):  
Radical Anion ◽  
Reduction Process ◽  
Kinetic Control ◽  
Peak Potential ◽  
Ketyl Radical ◽  
Aromatic Ketones ◽  
Experimental Parameters ◽  
Scan Rate ◽  
Kinetics Of ◽  
Electrochemical Carboxylation

The mechanism of the electrochemical carboxylation of several benzophenones (X-C6H4COC6H5; X = 4-OCH3, 4-CH3, H, 3-Cl, 3-CF3, 4-CF3 and 4-CN) and several ring-substituted acetophenones (Y-C6H4COCH3; Y = 4-OCH3, H, 3-OCH3, 3-Cl, 3-CF3, 4-CF3, 3-CN and 4-CN) has been investigated by cyclic voltammetry in dimethylformamide. In the presence of CO2, all compounds exhibit a single irreversible peak representing a 2 e reduction process. The reaction mechanism has been analysed using the dependence of the peak potential Ep on various experimental parameters such as the concentrations of the reactant, the scan rate and the temperature. Also the kinetics of the electrocarboxylation reaction has been examined. The whole set of results has been carefully analysed in the framework of an ECE-DISP mechanism. It has been found that, under the conditions employed, the electrocarboxylation reaction is always under a mixed ECE-DISP1 kinetic control. The first step of the reaction is an attack, via the oxygen atom, of the electrogenerated ketyl radical anion RR'CO•- at CO2. Further reduction of the carbonate-like adduct arising by such an attack followed by a second carboxylation reaction gives an arene-2-carboxylic acid.

scholarly journals Biomimetic Ketone Reduction by Disulfide Radical Anion

Molecules ◽  
2021 ◽  
Vol 26 (18) ◽  
pp. 5429
Author(s):  
Sebastian Barata-Vallejo ◽  
Konrad Skotnicki ◽  
Carla Ferreri ◽  
Bronislaw Marciniak ◽  
Krzysztof Bobrowski ◽  
...  
Keyword(s):  
Radical Anion ◽  
Radical Mechanism ◽  
Cyclic Ketones ◽  
High Concentration ◽  
Radical Chain ◽  
Ketyl Radical ◽  
Electron Reduction ◽  
The One ◽  
Key Steps ◽  
Radical Chain Reaction

The conversion of ribonucleosides to 2′-deoxyribonucleosides is catalyzed by ribonucleoside reductase enzymes in nature. One of the key steps in this complex radical mechanism is the reduction of the 3′-ketodeoxynucleotide by a pair of cysteine residues, providing the electrons via a disulfide radical anion (RSSR•−) in the active site of the enzyme. In the present study, the bioinspired conversion of ketones to corresponding alcohols was achieved by the intermediacy of disulfide radical anion of cysteine (CysSSCys)•− in water. High concentration of cysteine and pH 10.6 are necessary for high-yielding reactions. The photoinitiated radical chain reaction includes the one-electron reduction of carbonyl moiety by disulfide radical anion, protonation of the resulting ketyl radical anion by water, and H-atom abstraction from CysSH. The (CysSSCys)•− transient species generated by ionizing radiation in aqueous solutions allowed the measurement of kinetic data with ketones by pulse radiolysis. By measuring the rate of the decay of (CysSSCys)•−at λmax = 420 nm at various concentrations of ketones, we found the rate constants of three cyclic ketones to be in the range of 104–105 M−1s−1 at ~22 °C.

ChemInform Abstract: A Ketyl Radical-Anion “Triggered” [3,3]-Sigmatropic Shift.

ChemInform ◽  
2010 ◽  
Vol 29 (32) ◽  
pp. no-no
Author(s):  
E. J. ENHOLM ◽  
K. M. MORAN ◽  
P. E. WHITLEY ◽  
M. A. BATTISTE
Keyword(s):  
Radical Anion ◽  
Ketyl Radical ◽  
Sigmatropic Shift

Flash-photolysis study of the 4-(methyl sulphonate)-benzophenone ketyl radical anion in alcohol–water mixtures

1990 ◽  
Vol 86 (4) ◽  
pp. 619-622 ◽  
Author(s):  
Stephen W. Bigger ◽  
Robert A. Craig ◽  
Franz Grieser ◽  
Mirjana Prica
Keyword(s):  
Radical Anion ◽  
Flash Photolysis ◽  
Ketyl Radical ◽  
Alcohol Water
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