p‑TSA/Base-Promoted Propargylation/Cyclization of β‑Ketothioamides for the Regioselective Synthesis of Highly Substituted (Hydro)thiophenes

Metal-free, p-toluenesulfonic acid (p-TSA)-mediated, straightforward propargylation of β-ketothioamides with aryl propargyl alcohol has been achieved at room temperature. In addition, the reaction also provided thiazole rings as byproducts. Furthermore, the propargylated thioamides undergo intramolecular 1,5-cyclization to afford fully substituted (hydro)­thiophenes in the presence of base. Notably, the approach is pot, atom, and step economical (PASE).