Synthesis of 2-Oxy-3-(pyridinium-1'-yl)-1,4-naphthoquinone Derivatives by Iodine or Hydrogen Peroxide Oxidation of 1,4-Naphthoquinones in the Presence of Substituted Pyridines - Citterio, Attilio; Fochi, Mariacristina; Maronati, Antonietta; Sebastiano, Roberto; Mele, Andrea (Synthesis, 1997)