Synthesis of Unsymmetrical Bisindolylmethanes by Reaction of Indolylmagnesium Bromides with Sulfonyl Indoles

Sulfonyl indoles are widely recognized as alkylideneindolenine precursors amenable to provide functionalized indole derivatives upon reaction with nucleophiles. In this paper reaction of sulfonyl indoles with indolylmagnesium bromides is used to access unsymmetrical bisindolylmethanes. The target compounds are obtained in satisfactory yields starting from a wide range of substrate/reagent combinations. The utilization of pyrrolylmagnesium bromides for the same reaction also affords the expected adducts albeit in moderate yield.