Boron Trifluoride‐Mediated Synthesis of Oxazole N‐oxides

Abstract A new synthetic protocol for the preparation of oxazole N ‐oxides in the form of stable boron trifluoride complexes has been developed. It is based on the condensation of α‐diketone monooximes with an appropriate aldehyde component in the presence of an equimolar amount of boron trifluoride. The method opens access to a broad scope of derivatives including previously unknown 2‐unsubstituted oxazole N ‐oxides. Its abilities were demonstrated via the synthesis of 25 diverse oxazole derivatives in 14–89 % yields.