Formation and reactivity of .sigma.-radical cation intermediates in the carbon-carbon coupling reaction of phenyldiazomethanes by one-electron oxidation

One-electron oxidation of lphenyldiazomethanes afforded cis-stilbene predominantly. The reaction was independent of the oxidation mehtods, e.g., electrolysis, copper(II), triarylaminium salts, or photosensitized one-electron oxidations. The C-C coupling reaction was retarded by introducing α-substituents on phenyl-diazomethane. The ESR spectra of diazoalkane radical cations could be obtained during the electrolysis at low temperature and the resulting spectra revealed their unique electronic structure as σ-radicals for most cases