The article describes a new method for the preparation of four-membered cyclic sulfinamides using visible light energy transfer catalysis.[7] The authors assume that the previous methods provided mainly five- and six-membered cycles, while a specific approach to four-membered cyclic sulfinamides was lacking.[1][7] The described procedure uses photochemical activation of substrates, during which energy is transferred from the photosensitizer to the sulfinamide precursor, which enables the intramolecular formation of a four-membered ring.[7] The reaction proceeds under mild conditions and is designed to be compatible with a variety of organic groups on nitrogen and sulfur, thus expanding the range of available compounds.[7] The authors demonstrate that cyclic sulfinamides prepared in this way can be further chemically modified to other sulfur compounds with oxidation state VI, such as sulfoximines or sulfonimidamides, which are important in synthetic and pharmaceutical chemistry.[1][3] The study thereby provides a new platform for the rapid generation of libraries of structurally diverse sulfinamides that may be useful in the development of drugs and functional materials.[1][5][7]