Solid-phase lithiation of 5-carboxyindoles

Direct functionalization of protected 5-carboxyindole by metalation has been performed for the first time on solid-phase. The indole moiety has been tethered to aminomethylated polytetrahydrofuran cross-linked polystyrene, forming a secondary amide, which functions as a directing metalation group. The ortho-lithiated species have been quenched with substituted benzaldehydes affording resin bound alcohols. After cyclative cleavage regioisomeric mixtures of phthalides were obtained in the ratio 80:20.