Fast ring-opening of an intermediary α-stannyl-β-cyclopropylvinyl radical does not support formation of an α-stannylvinyl cation in the O-directed free radical hydrostannation of dialkyl acetylenes.

O-directed hydrostannation of beta-cyclopropyl propargyl alcohol 22 with stannanes and cat. Et3B in THF/H2O or PhMe/MeOH fails to deliver any detectable products of alpha-stannylvinyl cation capture. Instead only alpha-stannyl-beta-cyclopropylvinyl radical intermediates can be detected, which undergo fast H-atom abstraction and/or cyclopropane ring-opening as a result of eliminative beta-scission.