Peroxide Decompositions, II Dioxetans

There are two principal synthetic routes to dioxetans. The method introduced by Kopecky and Mumford [2] is the peroxide analogue of epoxide formation. 

Other cyclisation reactions lead to dioxetans and dioxetanones [2, 7]. The most convenient method is reaction of olefins with singlet oxygen [8, 9, 10]. Limitations of this method include olefins with insufficient reactivity and those having allylic H-atoms capable of taking part in the ene reaction which leads to allylic hydroperoxides. 

Exceptions to this rule are compounds of the diamantylidene type (59) they form 1,2-dioxetans with singlet oxygen in spite of the presence of allyUc hydrogen atoms because an ene reaction would produce a hydroperoxide with a very strained double bond (forbidden by Bredt s rule). 

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On the basis of mechanistic studies, mainly on these isolable cyclic four-membered peroxides (1 and 2), two main efficient chemiexcitation mechanisms can be defined in organic peroxide decomposition (i) the unimolecular decomposition or rearrangement of high-energy compounds leading to the formation of excited-state products, exemplified here in the case of the thermal decomposition of 1,2-dioxetane (equation l)11-15-19 and (ii) the decomposition of a peroxide, catalyzed by the interaction with a second compound, which is ultimately formed in its electronically excited state. 

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