Palladium-catalyzed cycloreductions of haloene-ynes in the presence of triethylsilane

Haloene-ynes 1 with a palladium catalyst would form the alkenylpalladium intermediates via intramolecular Heck reactions, which were reductively cleaved with triethylsilane or formate ligand to give the cycloreduction products 3 in good to excellent yields.