An approach to unsymmetrical 3,3′-diindolylmethanes through Pd-catalyzed cascade Heck cyclization of allenamides and o-ethynylanilines

Abstract

A highly efficient synthesis of unsymmetrical 3,3′-diindolylmethanes bearing various substituents has been developed by palladium-catalyzed cascade Heck/cyclization reaction. In this transformation, precursors allenamides and o-ethynylanilines were utilized to generate in situ indole skeletons. Modification of the methylene unit of diindolylmethane was achieved by treatment with oxidant and silyl nucleophiles. The methodology allows formation of one C–N bond, two C–C bonds and two new rings in one-pot.