Condensation Reactions of Aromatic Aldehydes with Active Methylene Compounds: The Beneficial Sinergy of Alkaline Ionic Liquid in One Pot Synthesis

Abstract

Background: In recent times, there has been on-going interest in developing convenient and environmentally friendly synthetic methods in organic chemistry. The use of ionic liquid catalysts in organic synthesis is a developing area that allows reactions to be run at low temperatures and without solvents. Literature overview revealed that room temperature supported ionic liquid catalysis is a developing field in catalytic science with huge application in organic synthesis. Hence in this current article, our focus is on the one-pot synthesis of arylidene derivatives with the use of ([bmim] OH) ionic liquid. Objectives: We describe here the use of an ionic liquid catalyst, 1-n-butyl-3-methylimidazolium hydroxide, [bmim] OH), in the convenient one pot synthesis of arylidene derivatives by the reaction of the active methylene compound, malononitrile, with pyrazole aromatic aldehydes under microwave irradiation. Methods: The functionalized ionic liquid, 1-n-butyl-3-methylimidazolium hydroxide ([bmim] OH), catalyzed Knoevenagel condensation reactions of pyrazole aromatic aldehydes with active methylene compound malononitrile carried out under microwave irradiation. The reaction progress was monitored by thin layer chromatography and the synthesized compounds were further characterized by NMR spectroscopy. Results: This proposed work demonstrates the utility of the use of the ionic liquid catalyst [bmim] OH, in the suitable, high yield (80-95%) microwave assisted reactions of pyrazole aromatic aldehydes with the active methylene compound, malononitrile. Conclusion: An eco-friendly synthesis of pyrazole derivatives has been demonstrated using ([bmim] OH) ionic liquid as a catalyst for the Knoevenagel condensation reactions of pyrazole aromatic aldehydes and malononitrile with microwave irradiation. The advantages of this green method are its convenience, mild reaction conditions, and high product yields (80-95%).