First reported propylphosphonic anhydride (T3P®) mediated Robinson–Gabriel cyclization. Synthesis of natural and unnatural 5-(3-indolyl)oxazoles

Abstract

In the present work, a propylphosphonic anhydride (T3P®) assisted Robinson–Gabriel cyclization of N-acyl-β-oxotryptamines for the synthesis of 2-substituted-5-(3-indolyl)oxazoles has been developed. The reactions proceeded smoothly in acetonitrile under microwave irradiation, and the product isolation required only an extraction and subsequent crystallization; no chromatography was necessary. The desired products were obtained in good to excellent yields.