Radical reactions ring closure, review

Pathways (la) and (Id) are the most frequent routes employed for the electrochemical generation of radicals. The radicals can be used in homocoupling, heterocoupling and addition reactions. In some cases these reactions have to compete with further oxidation or reduction of the radicals (see Sections 2.6.3.5 and 2.6.4.3). Electrogenerated radical ions (lb), (le), (If), cations (Ic) and anions (Ig) have been very efficiently used in electroorganic synthesis, e.g. for cathodic hydrodimerization, anodic dehydrodimerization, anodic substitution, cathodic cleavage or ring closure reactions [2, 5, 6]. These conversions are not treated in this review. 

No attempt has been made to provide the intensive detail found in Howard s review of oxyradicals [10], the review of Hendry et al. [43] of H-atom transfer to several radicals or Anbar and Neta s review of HO-radical reactions [44]. Instead, we have attempted to extend the scope of those reviews in two ways (i) rate coefficients are provided for R02-radical addition to many olefins, for ring closures to form cyclic ethers, and for intramolecular abstraction (ii) for each reaction, we have estimated the best value Arrhenius parameters (A-factor and E) and, where such values have been measured they are also listed. We believe the value of absolute rate coefficients is improved substantially by the availability of reliable Arrhenius parameters, with which one can calculate the values of rate coefficients at other temperatures for use in experimental or modelling studies. 

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