Synthesis of 2,5-Disubstituted Oxazoles and Oxazolines Catalyzed by Ruthenium(II) Porphyrin and Simple Copper Salts

A novel and moderate synthesis of 2,5-disubstituted oxazoles and oxazolines involving ruthenium(II) porphyrin copper chloride catalyzed cyclization was developed. These reactions using readily available benzene carboxylic acids and phenylethenes or phenylacetylenes are performed under mild conditions. The reactions proceed in series, giving rise to the formation of an intermolecular C-N bond and an intramolecular C-O bond, which yield oxazole or oxazoline derivatives simultaneously.