First Synthesis of Benzopyridoiodolium Salts and Twofold Buchwald-Hartwig Amination for the Total Synthesis of Quindoline

The first synthesis of cyclic benzopyridoiodolium salts is described. These hypervalent iodine intermediates are used in an efficient strategy for the construction of the δ-carboline core. This novel approach involves a twofold palladium-catalyzed Buchwald-Hartwig reaction between these unprecedented reagents and a primary amine. Our methodology successfully provides the expected N-substituted δ-carboline core and is efficiently applied in the total synthesis of quindoline.