PFAS, an organofluorine compound composed of fluorine and carbon atoms, is widely used in a variety of everyday products owing to its chemical resistance, nonflammability, water and oil repellency, and other properties. However, because of its high stability, it cannot be easily broken down in the natural environment. Moreover, when it accumulates in living organisms, it has harmful effects. As a result, regulations are in place on the production and use of PFAS, particularly in Europe and the United States, and the demand for alternatives to PFAS is increasing.
A research group led by Professor Norio Shibata of the Graduate School of Engineering at Nagoya Institute of Technology has suggested that tetrafluorosulfanyl (SF4) compounds, in which four fluorine atoms are bonded to a hexavalent sulfur atom, could replace PFAS as organic fluorine compounds with low environmental impact. The SF4 moiety, with its strong electron-withdrawing properties and high liposolubility, exhibits PFAS-like properties when incorporated into organic compounds. In addition, it has no carbon-fluorine bonds and is readily degradable, making it an environment-friendly alternative to PFAS. Until now, available methods for the synthesis of SF4 compounds have been limited; however, by applying cross-coupling reactions combining copper catalysts and aromatic diazonium salts, more than 50 SF4-acetylene substances have been successfully synthesized. The reaction takes only 30 min, and the resulting compounds can be molecularly transformed into more complex SF4 compounds.
Based on this approach, Shibata and his colleagues have also succeeded in synthesizing SF4 and SF5 fluorovinyls from SF4 acetylene. These compounds, which are not subject to PFAS regulations and are expected to have a wide range of applications as fluoropolymers, can contribute to the development of environment-friendly polymer materials and agricultural chemicals. In the future, they aim to create innovative products to realize a sustainable society via collaborative research with industry.
SF4-acetylene (left), SF4-vinyl fluoride (center), and SF5-vinyl fluoride (right) can be synthesized by this method
