Allylic Oxidation with Selenium Dioxide
Click the structures and reaction arrows in sequence to view the 3D models and animations respectively
The first step is a cycloaddition similar to the carbonyl ene reaction. The allylic seleninic acid produced in the first step undergoes a [2,3]-sigmatropic rearrangement to reinstate the double bond position. Rapid decomposition of the selenium (II) intermediate leads to an allylic alcohol. Oxidation continues to give the α,β-unsaturated carbonyl product.