Robinson‐Gabriel Oxazole Synthesis

Abstract The synthesis of 2,5‐ and 2,4,5‐substituted oxazole derivatives by the intramolecular condensation and dehydration of N ‐acyl α‐aminoketones in the presence of a dehydration reagent such as PCl 5 or sulfuric acid is known as the Robinson–Gabriel oxazole synthesis. Many cyclodehydrating reagents have been suggested for this reaction and polyphosphoric acid has been found to be the most suitable. This reaction has been applied for the syntheses of 2,5‐disubstituted and 2,4,5‐trisubstituted oxazole derivatives, especially for the syntheses of 2,5‐diaryloxazoles.