Inter- and intra-molecular aromatic N-substitution by arylnitrenium–aluminium chloride complexes generated from aryl azides in the presence of aluminium chloride

Abstract

Reactions of phenyl azide with aromatic compounds (i.e. benzene, toluene, ethylbenzene, cumene, anisole, and bromobenzene) in the presence of AlCl3 gave diarylamines, whereas those of phenyl azides with an electron-donating group such as Me and OMe yield little of the corresponding diarylamines (tar formation takes place). The reaction of 4-nitrophenyl azide with benzene in the presence of AlCl3 gave 4-nitrophenyl(phenyl)amine and a C-substitution product, 2-amino-5-nitrobiphenyl. Decomposition of 2-azidophenyl(phenyl)methane and 2-azidobiphenyls in CH2Cl2 in the presence of AlCl3 underwent an N-cyclization to afford 9,10-dihydroacridine and carbazoles, respectively, in good yields. The kinetic data on the decomposition of aryl azides and a Hammett plot (with ρ–6.0) for the formation of diarylamines suggest that the products are formed by an aromatic N-substitution of arylnitrenium–AlCl3 complexes via azide–AlCl3 complexes. We further argue the character of arylnitrenium–AlCl3 complexes.