Porous modified bentonite as efficient and selective catalyst in the synthesis of 1,5-benzodiazepines

Abstract

The synthesis of 1,5 benzodiazepine using natural and modified Argentinean bentonite (pillared layered clay and porous clay heterostructure) as catalysts through a condensation reaction between o-phenylenediamine (o-PDA) and excess of acetone as reactive and solvent at room temperature is reported. The catalysts were found to be highly active and selective, affording a high yield of the corresponding benzodiazepine. The effects of the modification of the natural bentonite and reaction conditions, such as temperature, time and amount of catalyst were investigated. The catalysts were also successfully employed for the preparation of other derivatives of 1,5-benzodiazepine using substituted o-PDAs and ketones. In all cases, the reactions are highly selective and are completed within 1-3 h. The catalyst showed excellent activity in all cases, showing 86-90% isolated yields of the corresponding derivatives of 1,5-benzodiazepine. The easy work-up procedure and the recyclable catalyst make this methodology attractive for large-scale operations.