Singlet oxygen phosphite-ozone adducts

There is a continuing interest in the use of phosphite-ozone adducts as sources of singlet oxygen and as reagents for mimicking the reactions of this species. The commercially available phosphite (54) forms an ozone adduct of striking stability. Decomposition of the adduct only becomes appreciable at temperatures > 0 °C the decomposition exhibits first-order kinetics, so that at 10 °C= 9.10 x 10 min and= 76.2 min. These... 

Scheme 12.17 gives some examples of oxidations by singlet oxygen. The reaction in Entry 1 was used to demonstrate that 102 can be generated from H202 and CIO-. Similarly, the reaction in Entry 2 was used to verify that the phosphite-ozone adducts... 

The reaction of singlet oxygen with conjugated double bonds usually is a 1,4-cycloaddition leading to formation of derivatives of the 1,2-diox -ene ring system. This can be achieved either by photooxidation or by reaction in the presence of triphenyl phosphite-ozone adduct (Section Vin.D.2), shown in equations 85 and 86 . ... 

The rather surprising observation has been made that gemacrene gives totally different products when it reacts with singlet oxygen, generated in a photosensitization reaction, than when it reacts with the triphenyl-phosphite-ozone adduct. There does not seem to be a clear-cut rationalization of this odd behaviour,... 

Anthryl ethers afford protection to alcohol functions treatment of the derivative with singlet oxygen, generated via the triphenyl phosphite-ozone adduct, followed by mild catalytic reduction, effects regeneration of the free alcohol (Scheme 136). 

Germacrene (318) reacts with the triphenyl phosphite-ozone adduct at —45°C at the 4,5-bond to give (319) after reduction, but with singlet oxygen initial attack occurs at the 7,13-bond, and further reaction gives the exocyclic... 

Decomposition of adducts such as triphenyl phosphite—ozone provides a convenient method for accomplishing chemical oxidations involving singlet oxygen and making it a useful oxygenating agent for synthetic and mechanistic appHcations. 

The bicyclic phosphite (11) with ozone gave a remarkably stable adduct (12) which decomposed to form singlet oxygen only above 0 °C. 

Singlet oxygen2 (see also Triphenyl phosphite ozonide, this volume). Dilute methylene chloride solutions of this reagent (1) react quantitatively at—78° with one equivalent of ozone to give the 1 1 adduct (2).s The adduct decomposes at room temperature to the phosphate (3) with evolution of singlet oxygen as shown... 

Singlet oxygen. Thompson1 reported that ozone and triaryl phosphites form 1 1 adducts which are stable at low temperatures when the temperature is raised the adducts decompose to triaryl phosphates and molecular oxygen. Murray and Kaplan2 reasoned that the oxygen formed should be in the singlet state and indeed found evidence for this assumption. Thus they were able to perform reactions... 

Another highly interesting reaction, in which singlet oxygen is formed, was described by Murray and Kaplan [440—442]. An adduct of triphenyl-phosphite and ozone is prepared at —70°C. It decomposes at a temperature as low as —35°C with the liberation of singlet oxygen namely... 

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