Copper, Silver and Sodium Salt-Mediated Quaternization by Arylation: Syntheses of N-Heterocyclic Carbene Precursors and 6-H-Phenanthridine Derivatives

We have developed a Cu-II-, Ag-I-, and NaOTf-mediated intramolecular quaternization by arylation reactions to synthesize a variety of N-heterocyclic carbene (NHC) precursors with a benzene-fused backbone. The methodology also provides a convenient alternative route for the synthesis of 6-H-phenanthridine derivatives. A novel silver-NHC complex was prepared by treatment of Ag2O with the free carbene, which was in situ prepared from the deprotonation of a representative quinazolinonium salt.