Practical synthesis of the rebeccamycin aglycone and related analogs by oxidative cyclization of bisindolylmaleimides with a Wacker-type catalytic system

Abstract Using atmospheric O 2 as the stoichiometric oxidant, Pd 2+ /Cu 2+ -catalyzed oxidative cyclization of the corresponding bisindolylmaleimides provides the rebeccamycin aglycone and related indolo[2,3- a ]pyrrolo[3,4- c ]carbazoles in 58–88% yield. The method is operationally simple and utilizes readily prepared substrates, making the process amenable to scaleup.