C-H functionalization/C-N bond formation: Copper-catalyzed synthesis of benzimidazoles from amidines

Abstract

(Chemical Equation Presented) Copper closes the ring: 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 (see scheme). © 2008 Wiley-VCH Verlag GmbH & Co. KGaA.