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 (see scheme).