Large Scale Synthesis of the High Quality Indoloquinone Antitumor Agent EO 9 via [Bis(trifluoroacetoxy)iodo]benzene Oxidation of 4-Aminoindole

A convenient large scale preparation of the indoloquinone antitumor agent EO 9 (1) has been developed. The hazardous reagent, Fremy's salt, was replaced by a safer one, [bis(trifluoro acetoxy)iodo]benzene, for oxidation of the 4-aminoindole 3 to the corresponding indoloquinone 4, and high quality 1 was easily obtained by choosing acetonitrile as the reaction solvent for substitution of the methoxy group with ethylenimine to introduce the aziridinyl group into EO 7 (6).