Visible‐Light Induced Oxidative Annulation of Enamides to 2,4,5‐Trisubstituted Oxazole Skeletons

Abstract A novel approach to various trisubstituted oxazoles (28 examples, up to 88% yield) has been developed via 9 H ‐thioxanthen‐9‐one (TX) mediated oxidative annulation of N ‐acetyl enamide under visible light irradiation in the presence of BF 3 ⋅ Et 2 O (2.0 equiv) and 40 mol% of PhNO 2 . This metal‐free procedure features high atom and step economy, green and mild conditions and broad substrate scope.