In this work, the novel approach via propylphosphonic anhydride (T3P®)-promoted synthesis of 1,5-benzodiazepines from o-phenylene-diamine, 5,5-dimethylcyclohexane-1,3-dione (dimedone), and aromatic aldehydes has been studied. The reaction conditions were optimized and the scope of the reaction was extended to various aromatic aldehydes. The synthesized compounds were obtained in reasonable to good