Mg and Zn Complexes with Phosphonate Substituted β-Octaphenylporphyrin as Photocatalysts for Oxidation of Sulfides

Magnesium 2,3,7,8,12,13,17,18-octa[(4-diethoxyphosphoryl)phenyl]porphyrinate (MgOPPP) was prepared in a good yield by reacting the free-base porphyrin with magnesium acetate in DMF at 130 °C. The resulting complex was used as a catalyst for the selective photocatalytic oxidation of sulfides to sulfoxides by molecular oxygen. Both dialkyl and alkyl aryl sulfides were almost quantitatively transformed into sulfoxides in an acetonitrile/water solvent mixture (5:1, v/v) under irradiation with blue LED (30 W), using a low loading of 0.05 mol% of MgOPPP as a photocatalyst. Comparative studies have shown that ZnOPPP also affords sulfoxides in quantitative yields and allows for shortening of the reaction time.