Meerwein arylation atom transfer reactions

Cyclizations of aromatic diazonium salts138 (intramolecular Meerwein arylations) are pieparatively related to atom transfer reactions because a radical cyclization is terminated by the transfer of an atom or group other than hydrogen. However, the two methods are not mechanistically related. In the atom transfer method, the atom that is transferred to the cyclic product always derives from the radical precursor, but in the cyclizations of aryldiazonium salts, die atom or group transferred derives from an added reagent. This means that many different products can be prepared from a single diazonium precursor, but it... 

The cupric halide-catalyzed reaction of an aryl diazonium salt with an olefin-known as the Meerwein arylation-is a powerful and well-developed method for the arylation of olefins (136, 137). Good results have been obtained for olefins bearing electron-withdrawing groups such as a carbonyl, a cyano, an aryl or an alkenyl group. Depending on the nature of the olefin and the diazonium salt, the reaction can lead either to the oxidation product 88 or to the Cl-atom transfer product 89 (Equation 13.10) [138]. 

---