Reactions of Indole with Hydroxyl Radicals and X-Ray Crystal Structure of a Novel Indole Trimer, 14-Acetyldiindolo [2, 3-a : 2', 3'-c] carbazole

Abstract

When indole reacted with titanium (III)- or iron (II)-hydrogen peroxide systems, the products varied widely, depending on the pH of the reaction solutions. Under acidic conditions, indole gave rise to oxindole, 2, 3'-biindole and a novel indole trimer, diindolo-[2, 3-a : 2', 3'-c] carbazole. Under neutral conditions, indole was converted to oxindole, hydroxyindoles and 3, 3'-biindole. The structure of the trimer was determined by X-ray diffraction analysis of its monoacetyl derivative. A possible mechanism for the formation of the products is proposed.