T3P-mediated microwave-assisted synthesis of oxazolopyridines

Abstract

In this work, we describe a convenient microwave-assisted synthesis of oxazolopyridines starting from aminopyridinols and carboxylic acids in presence of propylphosphonic anhydride (T3P). The method gives facile access to all regioisomeric oxazolopyridines bearing aliphatic or aromatic substituents in the 2-position. In general, the desired heteroaryls could be obtained in good yields between 65 and 88%. Even an oxazolopyridine with the bulky tert-butyl substituent is accessible in surprisingly good 49% yield. Oxazolo[5,4-c]pyridines were the only exception in this regard. Here the desired products could be synthesized only in 28 and 29% yield which is comparable to other published methods for this specific isomer.

Keywords

• Oxazolopyridine
• Heterocycle
• Microwave
• Condensation
• Drug design