Synthesis of 2,4,5-Trisubstituted Thiazoles via Lawesson’s Reagent-Mediated Chemoselective Thionation–Cyclization of Functionalized Enamides

An efficient route to 2-phenyl/(2-thienyl)-5-(het)­aryl/(methylthio)-4-functionalized thiazoles via one-step chemoselective thionation–cyclization of highly functionalized enamides mediated by Lawesson’s reagent is reported. These enamide precursors are obtained by nucleophilic ring-opening of 2-phenyl/(2-thienyl)-4-[bis­(methylthio)/(methylthio)­(het)­arylmethylene]-5-oxazolones with alkoxides and a variety of primary aromatic/aliphatic amines or amino acid esters, leading to the introduction of an ester, an N-substituted carboxamide, or a peptide functionality in the 4-position of the product thiazoles.