Intramolecular bromine-catalyzed aziridination: a new direct access to cyclic sulfonamides

N-Chloramine salts of ω-unsaturated sulfonamides have been prepared and shown to react in an intramolecular fashion in the presence of a catalytic amount of phenyltrimethylammonium tribromide to yield bicyclic aziridines. This intramolecular bromine-catalyzed aziridination procedure gave results complementary to those obtained by the copper-catalyzed methodology based on iminophenyliodinane.