Elements of Regiocontrol in the Direct Heteroarylation of Indoles/Pyrroles: Synthesis of Bi‐ and Fused Polycyclic Heteroarenes by Twofold or Tandem Fourfold CH Activation

Cross-coupling: the "chelation-directed control" and "catalytic-system-based control" strategies effectively switch the C2/C3-site selectivity in the heteroarylation of indoles and pyrroles with N-heteroarenes by a palladium-catalyzed twofold C-H activation to form biheteroarenes and are further extended to the synthesis of complex fused tri- and tetracyclic heteroarenes by a tandem fourfold C-H activation.