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

Abstract

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, 5wt% 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.