Copper(II) Trifluoromethanesulfonate Catalyzed Hydroamination Cyclization–Dimerization Cascade Reaction of Homopropargylic Amines for the Construction of Complex Fused Nitrogen‐Containing Tetracycles

A Cu(OTf) 2 ‐catalyzed cascade cyclization reaction of simple homopropargylic amines was developed. The sequence involved an intramolecular radical hydroamination cyclization followed by dimerization by a Povarov‐type reaction. Through this cascade reaction, a complex nitrogen‐containing tetracycle framework was constructed in one pot with the formation of four new bonds and five stereocenters. Noteworthy, the aglycon of the natural product incargranine B was facilely and efficiently synthesized by using this method.