Homolytic and heterolytic radical cleavage in the Kolbe reaction: Electrochemical oxidation of arylmethyl carboxylate ions

摘要: Abstract The mechanism of oxidative decarboxylation arylmethyl carboxylate ions is derived from the analysis cyclic voltammetric responses an extended series compounds, and, in a few selected cases, product distribution. In all removal first electron and cleavage bond that results formation CO2, are successive rather than concerted processes. majority unpaired located on carboxyl oxygen acyloxy radical which undergoes fast homolytic cleavage. reaction kinetically controlled by step. resulting alkyl formed so close to electrode surface it oxidized before having time dimerize thus yielding exclusively carbocation-derived products (non-Kolbe reaction). When aromatic portion ion easier oxidize, as with 4-dimethylamino-benzyl 9-anthracenyl-methyl derivatives, has zwitterionic character, slower follows heterolytic (involving intramolecular dissociative transfer). This reason kinetic control passes progressively also cause substantial amount dimer together products.