Ag-Catalyzed or Ag/PPh3‑Catalyzed Chemoselective Switchable Cascade Reactions of N‑Propargyl Thiocarbamoyl Fluorides and Malonate Esters

The divergent chemoselective synthesis of 2-methylene-2,3-dihydrothiazoles and 4-benzylidene pyrrolidine-2-thiones (most with E stereoselectivity) from N-propargyl thiocarbamoyl fluorides and malonate esters in moderate to excellent yields with a broad substrate scope and functional group tolerance has been accomplished. AgNTf2 catalyst at 60°C in dichloroethane provided 4-benzylidene pyrrolidine-2-thiones. AgOTf catalyst and PPh3 ligand in refluxing acetonitrile resulted in a complete switch in the reactivity of formed α,α-diester thioamide intermediates followed by isomerization to access 2-methylene-2,3-dihydrothiazoles.