Catalytic air oxidation of tertiary arylphosphines in the presence of tin(IV) iodide

Arylphosphines including Ph3P, o-C6H4(PPh2)2 and Ph2PCH2CH2PPh2 are cleanly and quantitatively converted into the corresponding phosphine oxides on reaction with dry air or dioxygen in CH2Cl2 solution in the presence of catalytic amounts of SnI4.