Abstract The reaction of gem-aryl-disubstituted methylenecyclopropanes with TiX 4/diethyl azodicarboxylate and TiX 4/diisopropyl azodicarboxylate in 1, 2-dichloroethane gave the dihalogenated ring-opened product, 2, 4-dihalobut-1-ene, in moderate-to-excellent yields under mild conditions. On the basis of the proposed Orton-type mechanism, we found that this reaction can also be carried out with free halogens such as bromine or iodine to give ...