Oxidative Nucleophilic Substitution of Hydrogen in Nitroarenes

Carbanions of 2‐phenylpropionitrile were found to add to nitroarenes in liquid ammonia to form σ H adducts, which were oxidized with KMnO 4 to yield products of oxidative nucleophilic substitution of hydrogen (ONSH) in the position para to the nitro group. Treatment of the carbanion‐nitroarene system with methyl iodide at ‐70°C indicated that the addition proceeds almost to completion. Thus, for the first time, the persistence of σ H adducts, formed between free anions and mononitroarenes, has been demonstrated. It was also shown that KMnO 4 oxidizes σ H adducts to nitrobenzene faster than it does carbanions. This selective ONSH in the para positions of nitroarenes is a general process. However, some substituents hinder or inhibit the oxidation step.