Product Study of Some One-Electron Oxidations of Bibenzyl and 4-Ethylbibenzyl. Evidence against Carbon-Carbon Bond Cleavage of the Bibenzyl Radical Cation in Solution

Article abstract of DOI:10.1021/jo00369a007

The oxidations of bibenzyl (1) and (or) 4-ethylbibenzyl (2) have been investigated under a variety of conditions, all of which should involve the intermediacy of bibenzyl radical cations: (a) reaction with ceric ammonium nitrate (CAN) in AcOH or CH3CN-H2O; (b) anodic oxidation in AcOH -CH3CN or (CH3)2CO-H2O; (c) photochemical oxidation by CAN in CH3CN; (d) photochemical autoxidation catalyzed by 9,10-dicyanoanthracene or by CAN in CH3CN.Nearly exclusive formation of side chain substituted products is observed for the chemical and electrochemical oxidations when the reactions are carried out in AcOH, CH3CN or AcOH-CH3CN, whereas extensive formation of C-C bond cleavage products occurs in the same processes when aqueous solvents are used.In the photochemical reactions, autoxidation produces both cleavage and side chain substituted products, whereas only the latter forms in the CAN-induced reaction in the absence of dioxygen.Evidence based on product analysis suggests that in these reactions no significant C-C bond breaking takes place at the state of bibenzyl radical cation.Cleavage products, where observed, nearly certainly derive from first-formed side chain substitution products