Polar Effects in Free Radical Reactions. Homolytic Aromatic Amination by the Amino Radical Cation, +NH3: Reactivity and Selectivity

Article abstract of DOI:10.1021/jo00197a030

Small amounts of Fe(II) salt initiate redox chains with hydroxyamino-O-sulfonic acid (HSA) and aromatic compounds leading to the amination of the aromatic ring.The positional and substrate selectivity with a variety of substituted benzenes show the important role of the electrophilic character of the radical <*>⁺NH3.Hammett relationships with ? and ?⁺ are roughly observed.The lower sensitivity to polar effects of the radical <*>⁺NH3 compared with (CH3)2⁺NH<*> is explained by the different reaction enthalpies.The different positional selectivity obtained with anisole and the redox system ⁺NH3OH/Ti(III) is discussed.