Chemo- and Stereoselective Synthesis of Substituted Thiazoles from tert-Alcohols Bearing Alkene and Alkyne Groups with Alkaline Earth Catalysts

We report here that thioamides can distinguish C–C double bonds and C–C triple bonds chemoselectively when subjected to a reaction with pent-1-en-4-yn-3-ol derivatives in the presence of Ca(OTf)2. This protocol offers a fast, efficient, and high-yielding synthesis of functionalized thiazoles. Interestingly, this reaction offers a time-dependent formation of kinetic and thermodynamic products. The products showed stereoselectivity concerning the alkene geometry. Further, we extended this protocol to synthesize oxazoles from propargyl alcohols and ibuprofen (NSAID) was converted into amide and then subjected to oxazole formation with tert-propargyl alcohols.