2,4-Disubstituted-5-acetoxythiazoles: useful intermediates for the synthesis of thiazolones and 2,4,5-trisubstituted thiazoles

A variety of 2,4-disubstituted-5-acetoxythiazoles were prepared from the substituted methyl benzoates in good to moderate yields using a three-step sequence: (1) ester to thionoester conversion, (2) coupling with an amino acid, and (3) acetic anhydride mediated cyclization. In situ hydrolysis and alkylation of 2,4-disubstituted-5-acetoxythiazoles afforded the corresponding thiazolones and 2,4,5-trisubstituted thiazoles. This methodology can be readily applied to the synthesis of thiazole-based chemical libraries.