Phosphine-Catalyzed\nCascade Cycloaddition of Vinyl\nOxiranes with Sulfonium Compounds to Step-Economically Construct Spiro-2(3<i>H</i>)‑furanone Scaffolds

In this work, we developed a phosphine-catalyzed cascade\nlactonization/[2\n+ 1] annulation reaction between vinyl oxiranes and sulfonium compounds\nfor the highly diastereoselective construction of spiro-2(3<i>H</i>)-furanone skeletons. The cascade cycloaddition proceeds\nvia the 2(5<i>H</i>)-furanone phosphonium intermediate,\nintroducing an oxygen-containing active intermediate for phosphine\ncatalysis. These findings highlight the significant potential of harnessing\nvinyl oxiranes as versatile synthons for constructing spirocyclic\ncompounds through simultaneous multicyclic skeleton formation.