Given the radical nature of intermediates in HAT-based reactions, Conditions B not surprisingly initiated intramolecular radical cyclizations of dienes to form new C-C bonds via cycloisomerization. Accordingly, methallyl prenyl malonate can undergo intramolecular cycloisomerization to yield the corresponding trisubstituted cyclopentane (26) malonate can be exchanged by an ether (27) or an amine (28) without compromising the high efficiency of the transformation. Endocyclic alkenes can be similarly used as effective cyclization partners to form the cis five-six bicyclic systems with high diastereoselectivity (29). Even a cyclic enol ether can be used as the radical acceptor (31). As shown in Table , the reaction shows high efficiency for 5-membered ring formation but is less suitable for formation of 6-membered rings (30), which gave only 50% yield along with a linear isomerization side-product.