Spiroazepinedione

The intramolecular version of this reaction gives tricyclic oxetanes such as 4 which undergoes acid-catalyzed rearrangement to give the seven-membered cyclic amide 5H4 86. The irradiation of a similar phthalimide derivative 6 gives a different product type, presumably by intramolecular oxetane formation 7 and metathetic cleavage to 888. Another side reaction results from intramolecular hydrogen abstraction, for example, 13 is formed via 12 from the imide 9 in addition to the expected main product spiroazepinedione 1189. 

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