Oxidation of olefins with 2-pyridineseleninic anhydride

2-Pyridineseleninic anhydride, prepared $\text{in situ}$ by oxidation of the corresponding diselenide with iodoxybenzene, is an efficient reagent for the conversion of olefins to unsaturated ketones with retention of the original position of the double bond. This reagent is, therefore, much more reactive towards olefins than benzeneseleninic anhydride. An explanation has been offered.