Radical cations: reactions of 2-phenylindole with aromatic amines under anodic oxidation. β-Scission of an amino alkoxy radical

Abstract

2-Phenyl-1H-indole reacts with p-anisidine, 2-nitro-p-anisidine and 2-nitro-p-methylaniline, under anodic oxidation, to give several products, depending on the potential used and on the presence or the absence of oxygen and a deprotonating agent. This investigation gives new insights into the reactivity of radical cations generated by a controlled anodic potential and neutral radicals corresponding to either 2-phenyl-1H-indole or to the three amines studied. The chosen amines show oxidation potentials lower (p-anisidine), equal (2-nitro-p-anisidine) or higher (2-nitro-p-methylaniline) than that of 2-phenyl-1H-indole and the reactions were carried out at the potential of the studied compounds. The oxidation of 2-phenyl-1H-indole in oxygen affords a new indole derivative, whose formation has been explained by β-scission of an indol-2-yloxyl radical and its structure was confirmed by X-ray analysis.