Singlet oxygen anion reaction

SCHEME 32. Anti selectivity for the singlet oxygen ene reaction of unsaturated systems bearing carboxylic acids and their anions... 

This group is prepared by the reaction of the anion of 9-hydroxyanthracene and the tosylate of an alcohol. Since the formation of this group requires an S 2 displacement on the alcohol to be protected, it is best suited for primaiy alcohols. It is cleaved by a novel singlet oxygen reaction followed by reduction of the endo-peroxide with hydrogen and Raney nickel. 

The elementary reaction step, which involves the formation of singlet oxygen, is a reaction of superoxide anion radicals CO ), which are the reaction intermediates of the above oxidation when performed in an alkaline medium. In the presence of water they may be converted to hydrogen peroxyl radicals HOO as follows ... 

Oxygen radical anion forms excited-singlet oxygen in different pathways, e.g. by a reaction with copper-cysteine-oxygen complex to yield the excimer (02)2- The computerized kinetic equations derived from this scheme allowed predictions in respect of the chemiluminescence intensity as a function of the oxygen and cysteine concentrations and as a function of time these were satisfactorily confirmed by the ex-... 

A photooxidative reaction in which molecular oxygen is incorporated into the reaction products(s). Three mechanisms appear to be common for such processes (a) reaction of triplet O2 with free radicals that have been generated photochemically (b) reaction of photochemically produced singlet oxygen with a molecular species and (c) the production of superoxide anion which then acts as the reactive species. See also Photooxidation... 

The reaction serves as an illustrative example of the synthetic utilization of the Te(II)—>Te(IV) two-electron shuttle. Another promising application is seen in photodynamic therapy in which tellurapyrylium dyes 119 can function as photosensitizers to produce either singlet oxygen or superoxide radical-anions (via electron transfer), thereby serving as cytotoxic agents. An important useful property of tellurapyrylium dyes is their absorbance in the near-infrared region where biological tissues are most important. 

Haag and Mill (1987) reported rate constants and correlation equations for oxidation of a series of phenylazonaphthol dyes, where oxidation of the naphthol and naphtholate ion are accounted for mainly by reaction with singlet oxygen, with some contribution from R02. Naphtholate anion is about ten times more reactive than naphthol toward oxidants. The correlation equations for these compounds are similar to those used for phenol oxidations (Tratnyek and Hoigne, 1991) ... 

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