Benzimidazoles are synthesized from amidines through a copper-catalyzed C–H functionalization/C–N bond-forming process. The method tolerates a broad range of functional groups and provides the benzimidazoles in up to 89 % yield. Best results are obtained by using 15 mol % Cu(OAc)2, 2–5 equivalents of HOAc as additive, and oxygen as the stoichiometric reoxidant.
“C–H Functionalization/C–N Bond Formation: Copper-Catalyzed Synthesis of Benzimidazoles from Amidines”, Angew. Chem. Int. Ed., 2008, 47(10), 1932-1934.