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

Abstract 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.