Molecular-iodine-catalyzed one-pot synthesis of 1,5-benzodiazepine derivatives under solvent-free conditions

2,3-Dihydro-1H-1,5-benzodiazepines have been synthesized from o-phenylenediamine (OPDA) and ketones under solvent-free conditions in the presence of a catalytic amount of molecular iodine. All of the ketones, including cyclic ketones and acyclic ketones, reacted smoothly with OPDA to furnish products. Compared to other reaction conditions, this new protocol has the advantage of excellent yield and short reaction time at room temperature.