Abstract
N-Arylhydroxylamines react with benzene in the presence of an acid. In the presence of trifluoroacetic acid (TFA), the reaction center is the nitrogen atom and nucleophilic attack by benzene proceeds at the nitrogen atom of the O-protonated N-phenylhydroxylamine. When TFA was replaced by trifluoromethanesulfonic acid (TFSA), the major products were aminobiphenyls. Together with the results obtained in the reaction of N, N-dimethylaniline N-oxide, it was demonstrated that the reactive intermediates are onium-benzenium ions which easily react with benzene and other aromatic compounds. Various iminium-benzenium ions were posturated in the reaction of nitroso-, azo-, azoxy-, and even nitrobenzenes with benzene. 1-Nitronaphthalene gave 1-(N, N-dihydroxyiminium)-benzenium ion in TFSA. The acid-catalyzed solvolytic reaction of O-aryl-N-acyl-or-N-sulfonylhydroxylamines formed highly delocalyzed phenoxenium ions, which react with nucleophiles such as benzene, phenol, anisole, alcohols, thiol, acetic acid, and acetonitrile. A few examples of synthetic application of these reactions were demonstrated : dibenzoazepines, aporysopine, aporphines, pyridocarbazole, orchinol and loroglossol were synthesized.
