1.2- Dioxetanones synthesis

This section details the methods of preparation that have been utilized over the last decade for the synthesis of 1,2-dioxetanes 1 and 1,2-dioxetanones 2 (rt-peroxy lactones). 

The only method for the synthesis of dioxetanones reported within the last decade relies on the cyclization of a-hydroperoxy acids. This method furnished the desired dioxetanones in reasonable yields and relies on removal of water by the use of a dehydrating reagent such as dicyclohexylcarbodiimide (DCC). For example, spiro-adamantyl dioxetanone was prepared in 55% yield utilizing this method (Equation 7) <1997JOC1623>. The reader is directed to CHEC-II(1996) <1996CHEC-II(1B)1041> for examples prior to 1996. 

Ten years ago Adam (Adam and Liu, 1972 Adam and Steinmetzer, 1972) reported the first synthesis and characterization of authentic dioxetanones, prepared by dehydrative cyclization of the corresponding a-hydroperoxy acids (26). They were shown to thermolyze as anticipated to carbon dioxide and the corresponding ketone with the concomitant emission of light. 

Usami K, Isobe M. Low-temperature photooxygenation of coelenterate luciferin analog — synthesis and proof of 1,2-dioxetanone as luminescence intermediate. Tetrahedron 1996 52 12061-90. 

In reactions like those discussed above, the dioxetanone is only assumed as an intermediate, although isotopic studies have confirmed this assumption in the case of the luciferins. However, they have been isolated as a result of rational synthesis. The first representative was obtained by Adam [14 a, 15] by singlet oxygen addition to a disilyl derivative of an ester. 

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