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

Abstract

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/Ph₃P/Et₃N 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/Ph₃P/K₂CO₃ 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.