Bimetallic Cu–Mn‐Catalyzed Synthesis of 2‐Arylquinazolin‐4(3H)‐ones: Aqueous Ammonia as Source of a Ring Nitrogen Atom

A new method for the synthesis of 2-arylquinazolin-4(3H)-ones that involves a three-component coupling reaction of 2-bromobenzamide, aryl aldehydes, and aqueous ammonia has been developed. This protocol employs Cu–Mn spinel oxide as a heterogeneous catalyst and does not require the presence of a ligand or external oxidant. Key features of the reaction include a recyclable catalyst, ligand-free conditions, and a wide scope of possible substrates. The mechanism begins with the replacement of the bromine atom with NH2 from aqueous ammonia followed by imine formation, intramolecular ring cyclization (C–N bond formation), and aromatization.