Cycloaddition nonconjugated olefins

Dilling, W. L. Intramolecular photochemical cycloaddition reactions of nonconjugated olefins. Chem. Rev. 66, 373 (1966). 

Formation of endoperoxides of type 178 can be interpreted as a L,4s + cycloaddition that involves singlet oxygen and therefore constitutes a photochemical reaction. Similarly, formation of hydroperoxides from nonconjugated olefins with an allylic hydrogen generally appears to be a concerted ene reaction as indicated in Scheme 65. Other mechanisms have... 

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