Annulative Coupling of β‐Ketothioamides with α‐Ester Sulfoxonium Ylides: A Practical Route to Functionalized Thiazolidine‐4‐Ones

A metal‐free annulative coupling strategy has been developed to synthesize functionalized thiazolidine‐4‐ones from β‐ketothioamides and α‐ester sulfoxonium ylides. This cascade process proceeds via concurrent CS and CN bond formation under mild conditions, delivering a wide range of thiazolidine‐4‐one derivatives in good‐to‐high yields. The method exhibits excellent functional group tolerance, broad substrate scope, and operational simplicity, with most products isolated via filtration without chromatography. The scalability and synthetic utility were demonstrated through gram‐scale synthesis and oxidative late‐stage functionalization, highlighting the potential of this strategy for accessing structurally diverse heterocycles.