o-Haloaryl allenylmethyl ethers and amines upon treatment with n-Bu 3 SnH and AIBN in refluxing benzene, underwent a 5-exo-trig free radical cyclisation to give the respective 3-ethenyl-2,3-dihydrobenzofurans and 3-ethenyl-2,3-dihydroindoles in good yields. © 1994 Georg Thieme Verlag. All rights reserved.