Acid‐Catalysed Cyclization ofo‐Aminobenzamide withα‐Oxodithioesters: A Divergent and Regioselective Synthesis of Quinazolinones and 1,3‐Benzothiazinones

Abstract Acid catalysed cyclization of o ‐aminobenzamide and α ‐oxodithioesters in a highly regioselective fashion to give 2‐aroylquinazolin‐4(3 H )‐ones and 2‐aroyl‐4 H ‐benzo[d][1,3]thiazin‐4‐ones by switching the reaction medium from DMF to acetic acid. Further, the generality of the stabilised protocols was tested with various functionalities. The range of yields for the quinazolinones and 1,3‐thiazinone are 57–67 % and 70–81 %, respectively. Probable mechanisms for the formation of the two series of products are proposed from control experiments.