A Pd-Catalyzed Combined α-Arylation/C-N Coupling Synthesis of Indoles

Significance

Barluenga and co-workers report an efficient and modular, one-pot synthesis of highly substituted indoles starting from o-dihalo­arenes 1 or 2-chloroarylsulfonates 4 and imines 2. The reaction involves two palladium-catalyzed processes: an imine α-arylation and an intramolecular amination, both promoted by the same catalyst. The scope of the reaction was extensively studied showing tolerance of a wide range of substituents at almost any position of either ring. Removal of the N-tert-butyl group to generate the free N-H indole was demonstrated using either TFA or AlCl₃ under both thermal and microwave conditions.