Highly Diastereoselective Dioxetane Formation in the Photooxygenation of Enecarbamates with an Oxazolidinone Chiral Auxiliary:  Steric Control in the [2 + 2] Cycloaddition of Singlet Oxygen through Conformational Alignment

The photooxygenation of oxazolidinone-substituted enecarbamates leads to diastereomerically pure dioxetanes. The high diastereoselectivity is rationalized in terms of effective π-facial control achieved by shielding one side of the double bond with the chiral auxiliary. The absolute configuration of the dioxetanes is assigned by derivatization to diols.