An efficient,environmentally benign,and solvent-free protocol for the synthesis of 4-substituted 1,5-benzodiazepines catalyzed by reusable sulfated polyborate

An efficient and environmentally benign method has been developed for the one-pot solvent-free synthesis of 4-substituted-1,5-benzodiazepines via three-component reaction of o-phenylenediamine, dimedone with a variety of aldehydes catalyzed by sulfated polyborate. The major advantages of the present method are good to excellent yields, shorter reaction time, simple experimental procedure, easy workup, solvent-free reaction condition, recyclability of the catalyst and ability to tolerate a variety of functional groups which gives economical as well as ecological rewards.