Palladium(II)-catalyzed tandem cyclization/C-H functionalization of alkynes for the synthesis of functionalized indoles.

A palladium-catalyzed tandem cyclization/C-H functionalization of two alkynes was accomplished to construct a series of polycyclic functionalized indoles. A range of internal alkynes bearing synthetically useful functional groups were tolerated. A good regioselectivity was observed when alkyl-substituted alkynes were introduced into the reaction system, and a single product was obtained. Molecular oxygen was used as the terminal oxidant in the approach, rendering the reaction more sustainable.