Synthetic approaches to 4,4-dimethyl-1,4-thiasilinane and its S-functional derivatives, 4,4-dimethyl-1,4-thiasilinane S-oxide, 4,4-dimethyl-1,4-thiasilinane S,S-dioxide, 4,4-dimethyl-1-(phenylsulfonylimino)-1,4-thiasilinane, and 1,4,4-trimethyl-1,4-thiasilinan-1-ylium iodide, were studied. The S-functional derivatives of 4,4-dimethyl-4-thiasilinane, unlike 3,3-dimethyl-3-thiasilinane, are hydrolytically stable.Thiasilinanes form an interesting class of heteroatomic cyclohexane derivatives. Thiasilinanes differ from earlier studied diheterocyclohexanes (dioxanes, dithianes, and oxathianes) in that they contain two heteroatoms of different nature: sulfur with a lone electron pair and silicon that exerts a strong inductive effect and, at the same time, has vacant d orbitals.Thiasilinanes have poorly been studied [136], while their S-functional derivatives have been unknown. In the course of the research into the properties and transformations of silathiacycloalkanes we have synthesized 3,3-dimethyl-1,3-thiasilinane S-oxide [7], 2,3,3-trimethyl-1,3-thiasilinane S-oxide, 2,3,3-tri-ÄÄÄÄÄÄÄÄÄÄÄÄ methyl-1,3-thiasilinane S,S-dioxide [8], 3,3-dimethyl-1-(phenylsulfonylimino)-1,3-thiasilinane, and 1,3,3-trimethyl-1,3-thiasilinan-1-ylium iodide [9, 10], and studied their transformations [10]. These works have primarily focused on 1,3-thiasilinanes; the only available information on 1,4-thiasilinanes related to the synthesis of 1,4-thiasilinane and its sulfonium salt, 1,4,4-trimethyl-1,4-thiasilinan-1-ylium iodide [4]. Proceeding with this research, in the present work we developed new synthetic approaches to 4,4-dimethyl-4-thiasilinane (I), synthesized their S-oxides II3V, and studied their hydrolytic stability.