Short oligo ethylene glycolic tailor-made ionic liquids as highly efficient and reusable catalyst for one-pot synthesis of 1,5-benzodiazepine derivatives under solvent free condition

•Tailor made short oligo ethylene glycolic dicationic RTILs were synthesized.•N-methyl imidazolium cations and acetate moieties as anions were used.•RTILs characterized by various methods & evaluated catalytic activity.•Catalytic activity of RTILs was tested for benzodiazepine synthesis.•Effects of different solvent system on catalyst were also determined.

Dicationic room temperature ionic liquids (RTILs) based on 1-methylimidazolium salts with varying their linkage chain between the cations were synthesized, characterized, and evaluated their catalytic activity for the synthesis of 1,5-benzodiazepine derivatives under solvent free mild reaction condition. On screening, all new synthesized imidazolium based dicationic RTILs showed efficient yields and selectivity of respective benzodiazepine. Especially, 5 wt% of tetraethylene glycol-bis (3-methylimidazolium) diacetate ([tetraEG(mim)2][OAc]2) was found to be the best dicationic RTIL as catalyst for this reaction. All these reactions were preceded very well under relatively mild reaction condition without addition of any co-catalyst and solvent. The present RTILs catalytic system compared with several homogeneous, heterogeneous catalysts. Moreover, effects of different solvent system on benzodiazepine reactions with these RTILs were also determined.

Graphical abstractShort oligo ethylene glycolic tailor-made ionic liquids as highly efficient and reusable catalyst for one-pot synthesis of 1,5-benzodiazepine derivatives under solvent free condition. Figure optionsDownload full-size imageDownload as PowerPoint slide