Solvent-Free Syntheses of 1,5-Benzodiazepines Using HY Zeolite as a Green Solid Acid Catalyst

1,5-Benzodiazepines are synthesized from 1,2-diamines and ketones catalyzed by HY zeolite at 50 °C under solvent-free conditions. This process offers an easy and efficient synthesis of substituted 1,5-benzodiazepines in high yields. The advantages of this protocol are operational simplicity, nontoxicity, low cost, easy recovery, and an environmentally benign nature. The catalyst is recovered by filtration and reused six times without significant loss in its catalytic activity. A plausible mechanism is also proposed.