Pd-catalysed intramolecular transformations of indolylbenzenesulfonamides: ortho -sulfonamido-bi(hetero)aryls via C2-arylation and polycyclic sultams via C3 arylation

Palladium-catalysed and base-dependent intra-molecular ipso -substitution and cyclisation strategies involving N -indolyl-substituted aryl-sulfonamides for the rapid construction of 2-aryl indole and indole-fused six-membered sultams are described. The Pd(OAc) 2 /Ph 3 P/Et 3 N combination delivers indolyl C2 arylated motifs via C(2)–N bond cleavage followed by C–C bond formation. In sharp contrast to this, the Pd(OAc) 2 /Ph 3 P/K 2 CO 3 combination induced intramolecular-Heck cross-coupling affords polycyclic sultams exclusively. Thus, this strategy is completely additive-dependent. It also shows a broad substrate scope and delivers the corresponding products in good to high yields.