Pd(II)/Ag(I)-Promoted One-Pot Synthesis of Cyclic Ureas from (Hetero)Aromatic Amines and Isocyanates

Abstract

A simple and facile one-pot reaction has been developed to afford a diverse range of N,N'-disubstituted benzimidazolones and imidazopyridinones containing two differently substituted N atoms. A cooperative Pd(II)/Ag(I) system promotes the sequential addition/intramolecular C-H amidation reaction of (hetero)aromatic amines and isocyanates, leading to the formation of two C-N bonds. A mechanism involving radical intermediates generated by single-electron transfer (SET) in the presence of a Ag2CO3 oxidant and Pd(OAc)(2) Lewis acid is proposed. This protocol offers an operationally easy, simple, and robust approach with the use of readily available starting materials, good functional group tolerance, and high efficiency.