Stabilizing effect of the tributylstannyl group on the adjacent carbon centered radicals has been studied. First, the intramolecular cyclization of vinyl radicals was carried out with N-aziridinyl imines as the radical acceptors. Allylic radicals, generated from the cyclization of vinyl radicals, gave two regioisomeric products, endo-cycloalkene as a major product along with exo-methylene cycloalkane as a minor product. But tributyltin substituted allylic radicals, generated from the cyclization of β-tributylstannyl vinyl radicals, gave only endo-cycloalkene. Second, when tributyltin substituted allyl iodides were treated with n-tributyltin hydride and AIBN, two regioisomeric products, allyl-and vinyl-stannanes were obtained in roughly equal ratio. Comparative study using trimethylsilyl substituted allyl iodide showed the similar result. Finally, radical induced ring opening of 3-substituted-1-tributylstannyl-2-vinylcyclopropanes was investigated. Treatment of vinylcyclopropanes with PhSH or $Bu_3SnH$ generated two intermediary carbon radicals, α to tin and β to tin. In case of R=H and Me, α-tributylstannyl carbon radicals were generated predominantly. On the other hand, β-tributylstannyl carbon radicals, followed by β-elimination of tributylstannyl radical, gave a conjugated dienyl product exclusively, when R is phenyl group. In a comparative study, i.e., when R is trimethylsilyl group, two carbon radicals, α to tin and α to silicon, were formed in roughly 1:2 rat10.
