Additions in presence of redox systems

Minisci, Galli and co-workers have studied a variety of radical reactions which result in the formation of organic azides. These processes commonly involve the interaction of an organic peroxide, an alkene, and azide ion in the presence of a ferrous-ferric redox system. The initial step is the reduction of the peroxide by Fe to form a free alkoxy radical (Fenton reaction, equation 104). 

The alkoxy radicals are electrophilic in character and react readily with conjugated olefins such as butadiene or cyclopentadiene  

In a similar reactioncyclohexanone peroxide forms e- .zido-caproic acid following ring fission of the original alkoxy radical to form an alkanoic acid radical (equation 108). 

The electrophilic nature of alkoxy radicals is evident from their reactions with olefins which are conjugated to electron-withdrawing substituents With such substrates, both a diazide and the 

In the presence of chloride ion, these reactions lead to the formation of chlorine atoms as well as azide radicals and the former react preferentially with organic (carbon) free radicals. This is demonstrated by the reaction of cyclohexanone peroxide with the ferrous-ferric system in presence of both azide and chloride ions to give exclusively -chlorocaproic acid (equation 111). This may be exploited syntheti- 

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