The sulfonyl radical-promoted cyclizations of 1,6-unsymmetrical dienes can be totally chemoselective. The addition of tosyl halides to various 1,6-dienes bearing both a nucleophilic and an electrophilic double bond clearly indicates that this attractive property is not related to the generally accepted electrophilic nature of tosyl radical. The chemoselectivity is likely to originate from the reversibility of the first step, i.e. tosyl radical addition to the double bond, which favors the formation of the adducts resulting from the one intermediate radical that cyclizes faster. © 1992, American Chemical Society. All rights reserved.