Carbon-Oxygen Bond-Cleavage Reactions by Electron Transfer. 3. Electrochemical Formation and Decomposition of the Diphenyl Ether Radical Anion

Article abstract of DOI:10.1021/ja00281a008

The electrochemical reduction of diphenyl ether to its unstable radical anion was observed at -2.95 V vs.SCE in dry N,N-dimethylformamide.Kinetic studies by cyclic voltammetry and homogeneous redox catalysis techniques resulted in a first-order rate constant of 4*E5 s^-1 for the decomposition of the radical anion of diphenyl ether.Controlled-potential electrolysis of diphenyl ether resulted in carbon-oxygen bond cleavage with quantitative formation of phenol and benzene.Electroreduction of diphenyl ether in the presence of D2O produced 15percent monodeuterium incorporation on benzene.The intermediacy of the phenyl radical in the cleavage pathway was tested by deploying an intramolecular radical trap, an o-(3-butenyl) substituent, on diphenyl ether.Electrochemical reduction of o-(3-butenyl)phenoxybenzene (1) in the absence of and in the presence of D2O confirmed the presence of the o-(3-butenyl)phenyl radical in the cleavage mechanism of the radical anion.Electroreduction of 1 in the presence of sodium isopropylate, a hydrogen atom donor, changed the product distribution ratio of 1-methylindan-(3-butenyl)benzene.The rate constant of the intramolecular cyclization reaction of the o-(3-butenyl)phenyl radical was estimated to be 1.5*E8 s^-1.