Cationic Arylation. II. Phenylation of Substituted Benzenes with Phenylazo-p-tolylsulfone in Acidic Solutions

The acid-catalyzed decomposition of phenylazo-p-tolylsulfone was studied in PhX, PhX-CH3CN and PhX-DMSO (X=OCH3, C2H5, CH3, Cl, CO2CH3, NO2). The decomposition was of first order but was faster with greater concentration of trifluoroacetic acid. The orientation and the partial rate factors for the phenylation of substituted benzenes were quite different from those for the radical phenylation but quite similar to those for the phenylation with phenyl cation generated from PhN2+BF4−. Experiments with deuterated compounds indicated that the abstraction of proton from the phenylated complex was not rate-determining. A mechanism involving phenyl cation was proposed for the acid-catalyzed decomposition of azosulfone.