The bromonium-promoted cyclization of conjugated aminodienes is described. The reaction proceeds smoothly in the presence of N-bromosuccinimide as halonium promoter, and using N-tosyl-protected aminodienes as substrates, to give the corresponding halocyclization products in high yields and with high diastereoselectivities. It can be envisaged that the formation of these products is the result of an S N 2Ј-type ring-opening of a terminal bromonium intermediate in a 5-4962 exo-trig or 6-exo-trig cyclization mode. The presence of an allyl bromide moiety in the haloamination products makes these molecules highly attractive from a synthetic point of view, as it opens the way for further transformations. Thus, allylic substitution reactions with different nucleophiles (acetate, azide, cyanide, and malonate), palladium-catalysed Suzuki coupling, and silver-mediated bromine displacement reactions were carried out successfully.General Procedure for the Bromoamination of Dienes: A solution of the aminodiene (0.2 mmol) in dry dichloromethane (0.7 mL) was added dropwise to a solution of N-bromosuccinimide (1.2 equiv., 0.24 mmol) in the same solvent (0.3 mL) under an argon atmosphere. The reaction mixture was stirred for 12 h at room temperature. After this time, the reaction was quenched by the addition of NaHCO 3 (saturated aq.; 2 mL). The organic phase was separated, and the aqueous phase was extracted with CH 2 Cl 2 (2 ϫ 3 mL). The combined organic extracts were dried (MgSO 4 ) and concentrated. The residue was purified by flash chromatography using hexane/ www.eurjoc.org