Copper(II)-Catalyzed Carbon–Carbon Triple Bond Cleavage of Internal Alkynes for the Synthesis of Annulated Indolizines

Cleavage of CC bond in butynedioates via copper­(II)-catalyzed reaction has been achieved, leading to the synthesis of benzo­[<i>f</i>]­pyrido­[1,2-<i>a</i>]­indole-6,11-diones in high yields by one-pot three-component reactions. In this unprecedented CC bond cleavage reaction of internal alkynes, both fragments from the alkyne are successively incorporated into the products