Polar Effects in Reactions of Carbon-Centered Radicals with Diazonium Salts: Free-Radical Diazo

Carbon-centered radicals react with diazonium salts by addition, leading under reductive conditions to azo derivatives (free-radical diazocoupling), or by electron-transfer in chain processes. The reaction is highly sensitive to polar effects and it has been investigated by three different processes: (i) alkyl radicals, generated from alkyl iodides, H2O2, Fe(II) salt, and DMSO, have been utilized to develop a new general synthesis of alkylarylazo compounds; (ii) the reaction of aryl radicals with diazonium salts in the presence of Ti(III) or Fe(II) salts has been investigated, also in relation to the fact that the reaction products (azoarenes and biaryls) are often detected as side products in classical organic reactions of diazonium salts, catalyzed by Cu(I) salts, such as the Sandmeyer, Meerwein, and Pschorr reactions; (iii) adducts from addition of aryl radicals to vinyl acetate or vinyl ether react with diazonium salts either by diazocoupling reaction or by electron-transfer; a general synthesis of [α-(acyloxy) alkyl]arylazo compounds has been developed.