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

Article abstract of DOI:10.1021/acs.orglett.6b03151

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.