N-Heterocyclic carbenes: Useful ligands for the palladium-catalysed direct C5 arylation of heteroaromatics with aryl bromides or electron-deficient aryl chlorides
Résumé
New Pd-N-heterocyclic carbene complexes have been prepared and employed for palladium-catalysed direct arylation of heteroaromatic derivatives by using aryl halides. These catalyst precursors promote the coupling of challenging aryl halides such as deactivated or congested aryl bromides and also activated aryl chlorides. This procedure employs only 1 mol-% of an air-stable palladium complex. This is a practical advantage over the procedures that employ palladium attached to air-sensitive phosphane ligands, which are often used to promote the coupling of such aryl halides.