[Phenoxenium ions: generations and reactions].

Abstract

The acid-catalyzed reaction of N-acyl- and N-sulfonylhydroxylamines with benzene proceeded smoothly to give C-C products; 2- and 4-hydroxybiphenyls. The reaction and the thermolysis of N-aryloxypyridinium salts involve common intermediates. The results of product analysis, the orientation of the reaction, effects of substituents on the nitrogen atom and on the phenyl ring suggested a mechanism involving a phenoxenium ion. The positive charge of the phenoxenium ion localized not on the oxygen atom but on the ortho and para carbons of the benzene ring. C-O product: diphenylethers are formed when the heterolysis of the N-O bonds is slow and the aromatic solvent has high nucleophilicity, suggesting an SN2-like reaction on the oxygen atom. The phenoxenium ions are also concerned with a rearrangement of O-arylhydroxylamine to 2-aminophenol. An ion-molecule pair involving phenoxenium ion and ammonia as an intermediate of the intramolecular ortho rearrangement.