Dioxetanes four-membered rings

If a four-membered ring peroxide (1.2-dioxetane) is involved in a reaction, its concerted bond cleavage into two carbonyl moieties should yield one of these in its excited electronic state on the basis of the orbital symmetry conservation rules of R. B. Woodward and R. Hoffmann ... 

As mentioned earlier (see p. 122) the previously postulated dioxetane intermediate in firefly bioluminescence has been challenged as no 180 is in-corporated in the carbon dioxide released during oxidation of firefly luciferin with 18C>2. In view of the crucial significance of the 180. experiments De Luca and Dempsey 202> rigorously examined the reliability of their tracer method. They conclude from their experiments that all available evidence is in favour of a linear, not a cyclic peroxide intermediate — in contrast to Cypridina bioluminescence where at least part of the reaction proceeds via a cyclic peroxide (dioxetane) as concluded from the incorporation of 180 into the carbon dioxide evolved 202,203). However, the dioxetane intermediate is not absolutely excluded as there is the possibility of a non-chemiluminescent hydrolytic cleavage of the four-membered ring 204>. 

Singlet oxygen reacts with electron rich or highly strained alkenes to form 1,2-dioxetanes. These four-membered ring peroxides decompose on warming to two carbonyl compounds (or moieties), usually with appearance of light emission (chemiluminescence). The macrocyclic bis-lactone in (6.17)608>, a musk fragrance, has been synthesized via such a sequence. 

The chemistry of some ring systems having two heteroatoms, i.e. dioxetanes, dithietanes, oxathietanes and thiazetidines are described. Next, the review considers compounds having either silicon or boron in a four-membered ring. Some thermolysis processes are interesting in the silicon series and the first thermally stable 1,2-dihydro-1,2-diborete is described. 

The following four-membered ring structures containing two oxygen atoms are known. Of these, the 1,2-dioxetanes 1 are most common and will form the majority of this chapter. 1,2-Dioxetanones 2 (a-peroxy lactones) and dioxetanimines 3 are rare but have been prepared and will be mentioned where relevant. 1,2-Dioxetenes 4, methylene-1,2-dioxetanes 5, and l,2-dioxetane-3,4-dione 6 have not been prepared in stable form and will only be discussed from a theoretical viewpoint. The isomeric 1,3-dioxetanes 7, l,3-dioxetane-2,4-dione 8, and methylene-1,3-dioxetanes 9 have also received attention from the theoretical viewpoint however, creditable chemical evidence for their existence is still lacking. 

Adam, W., in Four-membered Ring Peroxides 1,2-Dioxetanes and -Peroxylac-tones. The Chemistry of Peroxides, Patai, S. (Ed.), Wiley, New York, 1983, Chapter 24, pp. 829-920. 

Adam, W., Heil, M., Mosandl, T. and Saha-Moeller, C.R. (1992) Dioxetanes and a-peroxy lactones, four-membered ring cyclic peroxides, in Organic Peroxides (ed. W. Ando), John Wiley Sons, Chichester, UK, pp. 221-254. 

Their purification is equally problematic. In view of the thermal ability and ease of catalytic decomposition of the four-membered ring peroxides, many of the usual methods of purification are not applicable. This problem is more severe for the more labile a-peroxylactones than the 1,2-dioxetanes. To the best of our knowledge, no analytically pure a-peroxylactones have been prepared to date. ... 

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... 

Adam W. Four-membered ring peroxides 1,2-dioxetanes and a-peroxylactones. In Patai S. Ed. The chemistry of peroxide. New York Wiley. 1983 829-920. 

A conjugate addition reaction (Section 17.18) forms a dioxetane, which is a heterocyclic compound with a four-membered ring comprising two carbons and two oxygens. 

New examples of peroxymercuration continue to appear, particularly for the synthesis of cyclic peroxides. The first example of four-membered ring formation provides a novel synthetic entry into 1,2-dioxetans (Scheme 7). Allylic... 

The experimentally observed substituent effect on the triplet and singlet quantum yields in the complete series of methyl-substituted dioxetanes, as well as the predicted C—C and 0—0 bond strength for the four-membered peroxidic rings , have led to the hypothesis that a more concerted, almost synchronized, decomposition mechanism should lead to high excitation quantum yields (as in the case of tetramethyl-l,2-dioxetane), whereas the biradical pathway presumably leads to low quantum yields (as in the case of the unsubstituted 1,2-dioxetane)" . However, it appears that this criterion of concertedness is difficult to apply generally to structurally dissimilar dioxetane derivatives. 

Peroxide oxidation in the other compounds, on the other hand, generates a strained four-membered dioxetane or dioxetanone ring which, upon cleavage, releases its energy to the rest of the molecule or a fluorescent species present in the reaction medium. The light emitted in this case is from the fluorescent species as it returns to the ground energy state. 

Reviews on the following aspects of four-membered heterocycles have appeared 1,2-dioxetans and the reaction of singlet oxygen with alkenes/ /8-lactam antibiotics, small ring compounds of sulphur and selenium," recent developments in the synthesis of azetidines, the chemistry of benzazetes and of thiacyclobutenes (thietes) and their valence tautomers, and conformational barriers and interconversion pathways in some small ring systems. ... 

Dioxetanes are four-membered cyclic peroxides and their relative stability depends on the types of substituent groups present. Certain 1,2-dioxetanes are stable at room temperature but can be chemically triggered to produce chemiluminescence, these have an adamantyl group on one side of the ring and a... 

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