Metal-Free Oxidative C-H Amidation of N,N-Diarylureas with PhI(OAc)2: Synthesis of Benzimidazol-2-one Derivatives

Benzimidazol-2-ones have various biological functions and are usually prepared by reactions of substituted benzene-1,2-diamines with carbonyl-containing compounds or intramolecular N-arylations using substrates with carbon-halogen bonds. However, the starting materials of these protocols are often not readily available. Herein, a simple and practical metal-free oxidative C-H amidation of N,N-diarylureas has been developed that takes place at room temperature. This protocol uses readily available N,N-diarylureas as the starting materials and inexpensive PhI(OAc)(2) as the oxidant without the need of a catalyst, ligand, or the exclusion of air. The present method has a wide functional group tolerance and affords a new and practical strategy for the synthesis of N-heterocycles.