Abstract: Phosphonitrilic chloride was found to be an efficient reagent for the preparation of 1,5-benzodiazepine derivatives of o-phenylenediamine and ketones. This method is an easy, rapid, and high yielding reaction for the synthesis of 1,5-benzodiazepine derivatives. The remarkable advantages offered by this method include green and reusable catalyst, mild reaction conditions, fast reaction rate, and excellent yield of products. This novel methodology maintains atom economy and an environmentally friendly approach.