Visible‐Light‐Driven Persulfate Activation by <i>g</i> ‐C ₃ N ₄ for the Synthesis of 3‐Substituted‐2 <i>H</i> ‐Benzo[b][1,4]oxazin‐2‐Ones

In both industry and academia, the usage of readily available reagents and heterogeneous catalysts is crucial because they reduce labour and manufacturing wastes. Using persulfate (S 2 O 8 2 − ) and graphitic carbon nitride ( g ‐C 3 N 4 ) visible‐light photocatalysis, we herein describe a novel and one‐pot, two‐step synthetic methodology for the synthesis of a series of 3‐substituted‐2 H ‐benzo[b][1,4]oxazin‐2‐ones from aminoarenes and α‐oxocarboxylic acids. A radical pathway mechanism for the reaction has also been proposed based on control experiments. The condensation of aminoarenes with α‐oxocarboxylic acids produced the α‐imino acid, which was then subjected to intramolecular dehydrogenative lactonization in situ to provide the desired 3‐substituted‐2 H ‐benzo[b][1,4]oxazin‐2‐ones under the condition employed. Notable advantages of this method include the absence of metal‐ions, mild reaction conditions, gram‐scale applicability, suitability for natural product synthesis (e.g., cephalandole A), catalyst recoverability, and environmental friendliness.