Spiro-C(sp³)-atom transfer: Creating rigid three-dimensional structures with Ph₂SCN₂

The 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.