Aromatic substitution by N-arylhydroxylamines—II : Generation of nitrenes from arylhydroxylamines and N-benzenesulfonylhydroxylamines and phosphorous pentoxide

Substitution of benzene by N-benzene- and N-(4-methylbenzenesulfonyl)hydroxylamines occurs in the presence of phosphorous pentoxide whereas N-methyl-N-benzenesulfonylhydroxylamine gave no substitution product under the same conditions. When N-(4-methylbenzenesulfonyl)hydroxylamine was treated with phosphorous pentoxide in pyridine, N-(4-methylbenzenesulfonimido)pyridinium ylide was formed. Nitrene intermediates are postulated to account for these products. Similarly carbazole was formed from 2-hydroxylamino[1,1′-biphenyl] and phosphorous pentoxide but with phosphorous pentachloride, 3- and 3-chloro-2-amino[1,1′-biphenyls] were formed, most likely via a nitrenium ion intermediate.