Oxaziranes nitrones, rearrangement

The light sensitivity of nitrones in solution was observed by Kamlet and Kaplan, " who postulated the formation of oxaziranes. Krohnke formulated the rearrangement caused by light on a nitrone by using an oxazirane as an intermediate. Splitter and Calvin successfully isolated the rearranged products (9, 11, 12) and identified them as known oxaziranes [Eq. (6)]. 

The rearrangement of phenyl- er -butyl nitrone to the isomeric oxazirane (9) occurred in 95% yield on irradiation in acetonitrile for 2 hr. Because 2-ieri-butyl-3-phenyloxazirane (9) can be reconverted into the more stable nitrone, the photochemical reaction involves the conversion of radiation energy into chemical energy. 

---