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.