Spiro-C(sp<sup>3</sup>)-atom transfer: Creating rigid three-dimensional structures with Ph<sub>2</sub>SCN<sub>2</sub>.

Sun, Qiu; Belting, Jan-Niklas; Hauda, Julian; Tymann, David; Antoni, Patrick W; Goddard, Richard; Hansmann, Max M · Science · 2025

basic_science · Level V

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Abstract

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(sp<sup>3</sup>)-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 Ph<sub>2</sub>S=C=N<sub>2</sub> 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(sp<sup>3</sup>)-atom. New C-C and C-X (where X is O or N) bonds can be created around the C(sp<sup>3</sup>)-atom, which can ultimately be extended to four C-C σ-bonds in one step without resorting to transition metal catalysis. Ph<sub>2</sub>SCN<sub>2</sub> can also be used to access highly strained frameworks containing (oxa)spiro[2.2]pentanes as well as tricyclic spiro-compounds.