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

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. (C) 2013 Elsevier B.V. All rights reserved.