Three-Component Synthesis of Highly Functionalized 5-Acetyloxazoles

A study was conducted to demonstrate three-component synthesis of highly functionalized 5-acetyloxazoles. The two-step procedure allowed a highly flexible substitution pattern at C-2 and C-4 position. The synthesis procedure also allowed the incorporation of different substituents in 2- and 4-position of the resulting oxazoles. It was demonstrated that the acetyl group at C-5 was functionalized employing standard reactions. Enamide 5i was added in a sealed tube and dissolved in trifluoroacetic acid (TFA) to conduct the investigations. The reaction mixture was placed in a preheated oil bath (80 °C) and water was slowly added to the reaction mixture and extracted three times with CH 2Cl2 after stirring for 15 minutes. The reaction was performed with propiolic acid and pyruvic acid giving products with an alkynyl or an acetyl moiety in low yields.