Sun, QiuBelting, Jan-NiklasHauda, JulianTymann, DavidAntoni, Patrick W.Goddard, RichardHansmann, Max M.2025-02-212025-02-212025-02-21http://hdl.handle.net/2003/4348510.17877/DE290R-25318http:/dx.doi.org/10.1126/science.ads5974The introduction of a single C-atom into organic substrates typically results in the formation of flat molecules containing unsaturated C(sp)-centers. Adding a single C(sp3)-atom surrounded by four σ-C–C bonds, which opens up the three-dimensional space, is an unresolved problem in synthetic chemistry. We report the synthesis and application of the diazosulfur ylide Ph2S=C=N2 reagent that combines the reactivity of both sulfur ylides and diazo compounds to create carbon spiro-centers in a general fashion by the sequential or single-step installation of a C(sp3)-atom. New C–C and C–X (where X is O or N) bonds can be created around the C(sp3)-atom, which can ultimately be extended to four C–C σ-bonds in one step without resorting to transition metal catalysis. Ph2SCN2 can also be used to access highly strained frameworks containing (oxa)spiro[2.2]pentanes as well as tricyclic spiro-compounds.enhttps://creativecommons.org/licenses/by/4.0/540Article