Cycloaddition triplet oxygen

Cycloaddition of triplet oxygen with diradicals and latent... 

Acetyl peroxy nitrate, stmcture, 103, 104 Acetylsaturejol, triplet oxygen cycloaddition, 202, 204... 

Arylidene-,6-ionones, triplet oxygen cycloaddition, 199, 201 Aryl phosphites, ozone adducts, 732 Aryl-substituted olefins, selenide-catalyzed epoxidation, 384-5 Ascaridole... 

EPR see Electron paramagnetic resonance Ergosterol 3,6-acetate, triplet oxygen cycloaddition, 211... 

Peroxyketahzation, intramolecular, 276-7 Peroxyketals, triplet oxygen cycloaddition,... 

Kinetically stabilized azetes also show a high tendency for cycloaddition with a variety of other reagents. Cycloaddition of (47) with triplet oxygen produced a fully characterized dioxetan adduct (48), which decomposed at 25°C into t-butyl cyanide and the a-dione fragment (88AG(E)272). 

Highly strained alkenes often behave chemically as 1,2-diradicals, and can therefore readily react with triplet oxygen (Scheme 3.6). 1,2-Quinodimethanes can also react as diradicals, and can undergo a formal [2 + 4] cycloaddition with triplet oxygen to yield cyclic peroxides (first example, Scheme 3.22). That this reaction also proceeds in the dark strongly indicates that no singlet oxygen is involved [87]. 

The reaction pathway has been rationalized in terms of an attack of the triplet oxygen at the 5-position of (76) to produce the diradical (77) which may add to a second molecule of (76). The resulting peroxide (78) fragments to the dithiobenzoic acid derivative (79) which may act as a dipolarophile in the last step of the [3 + 2] cycloaddition reaction of (76). The structure of the final product (80) was established by X-ray analysis (81CB285). 

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