Palladium(II) N-heterocyclic carbene complexes as catalysts for the direct arylation of pyrrole derivatives with aryl chlorides

Abstract

Silver(I) N-heterocyclic carbene complexes were synthesized in good yields by the reactions of 1,3-dialkylperhydrobenzimidazolyum salts with silver(I) oxide and used as transmetallation reagents for the synthesis of palladium(II) N-heterocyclic carbene complexes. All of the complexes were characterized using elemental analysis, H-1 NMR and C-13 NMR spectroscopy. The catalytic activity of Pd(II)-NHC complexes in the direct arylation of pyrrole derivatives was investigated. These Pd(II)-NHC complexes showed the good catalytic performance for the direct arylation of pyrrole derivatives with readily available and inexpensive aryl chlorides. The arylation reactions regioselectively produced C2- or C5-arylation products in moderate to good yields by using 1 mol% of the palladium complex.