The mechanism of the novel dimethyldioxirane (DMD) oxidation of sigma(H) adducts (Meisenheimercomplexes) generated from nitroarenes and carbanions was elucidated. The proposed mechanism, which is akin to that of the oxidative Nef reaction, is supported by the isolation of the cyclohexadienone intermediate and the lack of a primary kinetic isotopic effect. Protic solvents (H(2)O, MeOH) enhance the
DMD Oxidation of <b><i>in-Situ</i></b>-Generated σ<sup>H</sup> Adducts Derived from Nitroarenes and the Carbanion of 2-Phenylpropionitrile to Phenols: The First Direct Substitution of a Nitro by a Hydroxy Group
The dimethyldioxirane (DMD) oxidation of sigma(H) adducts derived from nitroarenes and the carbanion of 2-phenylpropionitrile yields unexpectedly the phenols 5 as the major products, while the usually observed nitroarenes 4 are formed in very little amounts, if any. The phenol yield was much improved when a small quantity (0.5-1.0 equiv.) of water was added at the start of the reaction. This novel oxidation of Meisenheimer complexes provides the first direct synthesis of phenols from nitroarenes, an unprecendented transformation.