Group transfer reactions at secondary positions generally occurred notably faster in cyclic systems (6ae) than in open-chain counterparts (6f-j). The slower reaction rates of open-chain systems could be attributed to their higher entropic degrees of freedom. We were happy to observe that the radical group transfer reaction occurred with high diastereoselectivity in cyclic systems 6a-6d, while open-chain systems 6f-6g produced 11-15% of a minor diastereomer. Reaction at primary positions (6k-p) was slow and gave low to moderate yields, despite complete consumption of the substrates. Primary alkyl radicals are known to be unstable due to a lack of hyperconjugative donation of electron density from adjacent alkyl groups. This can result in a higher activation energy for the formation of such radicals, thereby explaining the longer reaction times. Benzylic radicals, on the other hand, are known to be stabilized by delocalization. Indeed, we were pleased to observe rapid reaction and high isolated yields at benzylic positions (6q-s). Similarly, reactions at electron-deficient positions also proceeded rapidly and gave high yields (6t-v). This has been attributed to the ease of single-electron reduction of activated carbon-iodine bonds in substrates 4q-v. The resulting radical intermediates, moreover, are electrophilic, and thus polarity-matched for reaction with the electronrich vinyl silane moiety. Interestingly, the radical alkene group transfer in open-chain benzylic and electron-deficient systems 6q-6v proceeded with high diastereoselectivity. A similar effect has been reported previously in group transfer reactions of other vinyl silanes with electron-deficient radicals. We were pleased to obtain the β,γ-unsaturated carboxylic acid derivatives 6t-u with no migration of the double bond. Only in ketone 6v did we observe elimination of the intermediate homoallylic alcohol to produce a conjugated system.