Radical cation ester cleavage in solution: mechanism of the mesolytic O-CO bond scission.
A wide range of enol carbonate, carbamate, and ester radical cations is characterized in solution by cyclic voltammetry and EPR spectroscopy. Preparative transformations using one-electron oxidants or anodic oxidation yield benzofurans after O-CO bond cleavage. Mechanistic investigations and direct detection of radical intermediates reveal that all enol radical cations undergo exclusively O-CO bond cleavage to provide alpha-carbonyl cations and acyl (or alternatively, alkoxyacyl and aminoacyl) radicals, respectively. The kinetics of the mesolytic fragmentation and the influence of nucleophilic additives have been determined using fast-scan cyclic voltammetry.
Schmittel
M
M
FB 8 - OC1 (Chemie-Biologie) der Universität-GH Siegen, Adolf-Reichwein-Strasse, D-57068 Siegen, Germany. schmittel@chemie.uni-siegen.de
Peters
K
K
Peters
E M
EM
Haeuseler
A
A
Trenkle
H
H