直線的分子連結を実現するテトラフルオロスルファニル化合物群：合成と開拓

Abstract

Isosterism and bioisosterism are concepts in molecular design of specialty materials and drugs compounds. Fluorine and fluorine-containing functional groups are often used as isosteres and bioisosteres. Fluorine atom (F) is the most suitable isostere of hydrogen atom (H). With regard to electronegativity, fluorine is also used as a good substitute for hydroxyl (OH) group. Trifluoromethyl (CF3) group can be used as an equivalent for methyl or isopropyl groups, and difluoromethyl (-CF2H) group is an alcohol (-OH) equivalent. Pentafluoro-λ6-sulfanyl (SF5) group has recently attracted attention as a super CF3 group. This review introduces an undeveloped fluorine-containing functional group, tetrafluoro-λ6-sulfanyl (SF4) moiety. The SF4 is a unit consisting of four fluorine atoms bonded around an octahedral sulfur (VI) atom, with strong electron-withdrawing property and high lipophilicity. Characteristic of the SF4 unit are the cis- and trans-geometries connecting the two fragments. Interestingly, the trans-SF4 unit can connect two separated parts in a linear (180°) configuration via an octahedral sulfur center. Although organic compounds having an SF4 unit were known as early as the 1950s, their synthetic studies have been largely underdeveloped. We herein describe the structural and chemical characteristics of SF4-containing compounds, the background of the synthetic study, and their state-of-the-art synthetic constructions.