Oxidative trimerization of indole: on the formation of dications and radical cations by reaction of indole and nitrosobenzene in the presence of acids

The reactions of indole with nitrosobenzene in the presence of acetic, mono chloroacetic, monobromoacetic and trichloroacetic acid afford as the main p roduct a deep-green precipitate, which in a preceding study had been errone ously identified as the aminyl radical of a trimer indole. The identity of the minor products was confirmed. This paper deals with the determination o f the correct structure of the compounds contained in the precipitate throu gh a study based on chemical reactions, electrochemical measurements and X- ray analysis.