Oxidative cyclization of acyclic ureas with bis(trifluoroacetoxy)iodobenzene to generate N-substituted 2-benzimidazolinones

A facile method to synthesize N-substituted 2-benzimidazolinones from secondary aromatic amines is presented. Sequential treatment of a secondary aromatic amine with phosgene and methoxylamine afforded an acyclic 3-substituted 3-aryl-1-methoxy urea. Brief exposure of this urea to bis(trifluoroacetoxy)iodobenzene induced an oxidative cyclization to the ortho-position of the benzene ring, resulting in the formation of a 3-substituted 1-methoxy-2-benzimidazolinone. Hydrogenation over Pd/C cleaves the methoxy group to afford the N-substituted 2-benzimidazolinone.