Stepwise Multiple Arylation of 1H-Pyrroles via Ligand-Controlled Palladium Catalysis

Unsymmetrical 2,5-diaryl-1H-pyrroles can be synthesized via the C5-selective arylation of N-unprotected 2-aryl-1H-pyrroles using a palladium catalyst. A one-pot, stepwise multiple arylation of nonsubstituted 1H-pyrrole can also afford these unsymmetrical pyrroles. Furthermore, trisubstituted pyrroles with three different aryl groups can be successfully obtained by site-selective arylation of these pyrroles. Use of appropriate ligands successfully provided 2,2,5-triaryl-2H-pyrroles and 2,3,5-triaryl-1H-pyrroles, respectively.