Sulfide‐Catalyzed Diastereoselective Spirocyclopropanation: Constructing Spiro‐cyclopropanyl‐pyrazolones From α‐Arylidenepyrazolones

An efficient and diastereoselective [2+1] annulation of arylidenepyrazolones with bromides has been developed that relies on in situ formation of sulfur ylide via a direct sulfide‐catalyzed process. A variety of spirocyclopropanyl pyrazolones were achieved in good to excellent yields (up to 93% yield) with high diastereoselectives (up to 20 : 1 dr). Meanwhile, several spirocyclopropanyl compounds were also prepared from corresponding enones. This catalytic strategy exhibits good functional group tolerance, gram‐scale capacity and broad substrate scope, and provides various spirocyclopropanyl derivatives. An efficient and diastereoselective [2+1] annulation of arylidenepyrazolones with bromides has been developed that relies on in situ formation of sulfur ylide via a direct sulfide‐catalyzed process.