The synthesis of a series of unsaturated 4-methylene-1,3-dioxolanes has been realized and the addition of thiophenol to the synthesized compounds in the presence of radical initiators has been carried out. It has been established the behavior of the addition reaction both with opening of dioxolane cycle and without it. The influence of nature of substituents of С2-carbon atom of dioxolane cycle, ratio of the initial reagents and temperature on direction of the addition reaction has been studied. The adducts obtained as a result of the addition reaction have a linear and cyclic structure, which have been established by data of the chemical and spectral analyses. It has been found that the ratio dioxolane compound: thiophenol, reaction temperature and nature of the functional substituent influences on quantity of these adducts.