1.2- Dioxetane ring

The mechanism of 1,2-dioxetane formation in the reaction of lucigenin with hydrogen peroxide suggests a nucleophilic attack of peroxide anion on position 9 of the acri-dinium ring, followed by deprotonation and subsequent formation of 1,2-dioxetane ring... 

Chapter 4 deals with the chemistry of the energy-rich 1,2-dioxetane ring system the isomeric 1,3-dioxetane systems still await exploration. The exploration of 1,2-dioxetane chemistry is also of recent vintage and the fact that they are cyclic peroxides explains their high reactivity. It is now established that such heterocycles are involved in bioluminescence. 

Baumstark AL. The 1,2-dioxetane ring system preparation, thermolysis, and insertion reactions. In Frimer AA ed. Singlet 02 Vol II. Boca Raton CRC, 1985 1-35. 

Dioxetane ring s. 30, 86 also oxirane ring, effect of different sensitizers, solvents, and additives, s. C. W. Jefford and A. F. Boschung, Tetrah. Let. 1976, 4771... 

H and 13C chemical shifts of dioxetane ring atoms (ppm with respect to TMS). 

Fluoride-induced deprotection in the unusual substrate 176 was accompanied by 0-0 cleavage in the dioxetane ring to give benzodioxole 177 (Equation 51) <1997TL8947>. 

It has been suggested that the more easily the dioxetane ring can be puckered, the lower its thermal stability. This could be the reason for the high activation energies of cyclobutadienedioxetane (Entry 23 in Table 4) and diadamantylidenedioxetane (Entry 30 in Table 4). However, why should the tetraethyldioxetane (Entry 25 in Table 4) be more planar and more rigid than tetramethyldioxetane (Entry 19 in Table 4)7 Clearly, we do not as yet understand the thermal stability of 1,2-dioxetanes and much has yet to be learned. X-ray structure data would seem important on this problem. 

Besides their thermal decompositions into carbonyl fragments, the chemistry of 1,2-dioxetanes is quite limited. Obviously one of the reasons for this is the great lability of the dioxetane ring system. However, a number of reactions with nucleophiles and electrophiles have been performed and will be briefly reviewed here. 

Dioxetane substrates for alkaline phosphatase and p-galac-tosidase The four-membered ring peroxides, 1,2-dioxetanes, are too unstable to be used as chemiluminescent substrates due to their low energy of activation (Adam and Cilento, 1983). Substitution of the carbonyls in the dioxetane ring has substantial effects on the rate of decomposition (Wieringa et al., 1972), i.e., half-lives from less than a second for simple dioxetanes to over 21 years for some of the... 

Chemically initiated electron-exchange luminescence (CIEEL) constitutes a general phenomenon, the important example of which is the firefly bioluminescence. A longstanding mechanistic dichotomy on the CIEEL process concerns concerted versus stepwise cleavage of the dioxetane ring. As it is shown in Scheme 1 (on the left), the... 

For a new dioxetane with fused furan ring, steric repulsion between t-butyl and methyls should prevent twisting of the dioxetane ring so that the dioxetane becomes stable. 

One of the most powerful techniques to characterize 1,2-dioxetanes has been proton NMR. Thus, resonance of the dioxetane ring protons which are alkyl substituted are observed at 4.9-5.2 ppm.12 14,16 Dimethylamino substitution as in lw does not alter the chemical shift, since the ring proton resonance still occurs at 4.90 ppm.36b However, alkoxy substitution deshields the ring proton significantly, and the resonance occurs at 5.6-6.8 ppm.34 Aryl and olefinic substitution also shift the resonance to lower field, occurring at 5.6-5.9 ppm.14 36,37... 

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