1,2-Dioxetanes substitution patterns

Eq. 63. Although obvious exceptions are evident in Table 4, the effect of substitution patterns, that is, symmetrical vs. unsymmetrical, is dramatic. The reasons for this are as yet not understood, but might be connected with the problem of energy partitioning since two different carbonyl fragments can be excited in unsymmetrical dioxetanes. 

Hoshiya N, Watanabe N, Ijuin HK, Matsumoto M. Effect of intramolecular hydrogen bonding on thermolysis of dioxetane unusual instability of bicyclic dioxetanes bearing a hydroxynaphthyl group with vicinal substitution pattern. Chem Lett 2007 36 516-7. 

Fig. 40. Chemiluminescent decomposition of adamantyl aromatic dioxetanes by fluoride-induced cleavage of silyl ether side chains. The 2,6-substitution pattern shown in (a) has a quantum efficiency of 0.01%, whereas the 2,4-substitution pattern shown in (b) has a quantum efficiency of 45%. The data [which are taken from the work of Schaap et al. (S8)] can be rationalized by considering the mechanism suggested in Fig. 39.

In conclusion, we have discovered that chelation with alkaline metal ion, especially Li+, enhances markedly chemiluminescence efficiency of CTICL for an even pattern hydroxyaryl-substituted dioxetane, i.e., bicyclic dioxetane bearing a 3-hydroxynaphthalene-2-yl group 1 in THF. 

For similar substrates, such as substituted styrenes, stilbenes, or 1-vinylthiophenes, in some cases bis-endoperoxides have been isolated similar to the indene and dihydronaphthalene cases vide infra). Also, terpene derivatives are a treasure house of polyfunctional substrates for which aU types of reaction modes have been observed. Substituted 3-vinylindoles 48 without aUyhc hydrogens give with Oj the endoperoxides 49 by [4 -I- 2]-cycloaddition unless the s-cis conformation is disfavored due to the substituent pattern. Product 50 is formed presumably by [2 -I- 2]-cycloaddition of singlet oxygen and subsequent 1,2-dioxetane cleavage. 

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