Organosilver(i/ii) catalyzed C–N coupling reactions – phenazines

Abstract

The paper reports organosilver catalyzed C–N coupling reactions of pyridyl (py) carbaldehydes and substituted anilines, thereby producing substantially different phenazines (PZs) with basic molecular skeletal and bulk N_py-substituents. The different chemical reactivity of N_py-substituted derivatives in polar protic solvents, in the presence of the Ag^I-salts, with the dinuclear silver(I/II) organometallic precursors exhibiting C–Ag^I/II–Cl covalently bonded species, is described. The latter are elucidated fully by the theoretical quantum chemical method and experimentally evidenced by mass spectrometry in the gas phase (GP), involving a variety of ionization techniques. To our knowledge, we first report a comprehensive study of the nature of the organometallic precursors, which represents an important step of the catalyzed C–C and C–N coupling processes. Thus impacting all fields the enormous synthetic research efforts are focused on PZs, which through the diversity of the molecular architectures are main components observed in naturally occurring products (NPs), dyes, pesticides, antibiotics, etc. The emphasis of the paper is on the mass spectrometry (MS), employing its high-resolution power and accuracy of the analytical qualitative, quantitative and structural information as well as the physico-chemical thermodynamic one, at the analyte concentrations in the range of fg g⁻¹. The latter, which are beyond the capability of other instrumental methods for structural analysis, make the MS an irreplaceable method in the advanced catalytical research. Its combined application with the method of the quantum chemistry provides reliable thermodynamic information in the condensed phase and in the GP, which helps understand comprehensively the mechanisms of the organometallic catalyzing processes, particularly the unique coupling reactions, thus improving significantly their effectiveness.