Organocatalytic Cyclization of COS and Propargylic Derivatives to Value-Added Heterocyclic Compounds

The organocatalytic cyclization of propargylic amines/amides with carbonyl sulfide (COS) was firstly achieved by employing COS adducts of Lewis base (LB) as organocatalysts, affording various functionalized 1,3-thiazolidine-2-ones, and 1,3-thiazolidine-2,4-diones derivatives in a highly chemo- and stereoselective manner. The isotope labeling and stoichiometric experiments suggested the LB-COS adducts preferentially mediated basic ionic pair mechanism. Furthermore, the practical application of this methodology was highlighted by the highly efficient synthesis of rosiglitazone using COS as sulfur source.