Three-component coupling reactions in ionic liquids: an improved protocol for the synthesis of 1,4-dihydropyridines

Abstract

Three-component condensation of aldehyde, β-ketoester and methyl 3-aminocrotonate proceeds smoothly in 1-n-butyl-3-methylimidazolium tetrafluoroborate [bmim]BF₄ or 1-n-butyl-3-methylimidazolium hexafluorophosphate [bmim]PF₆ ionic liquids at room temperature under mild conditions to afford the corresponding 1,4-dihydropyridine derivatives in high yields. The recovered activated ionic liquids are recycled for four to five runs with no loss in activity.