It′s no sacrifice: Alkynes have been used as direct precursors to sulfur ylides under gold or platinum π-acid catalysis in an atom-economic manner. An intramolecular redox reaction between an alkyne group with a tethered sulfoxide unit generates a sulfur ylide, which undergoes 2,3-sigmatropic rearrangement. Acyclic substrates are cycloisomerized to afford functionalized dihydrothiophenones (see scheme) and dihydrothiopyranones.
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