Three-component Synthesis of Tetrahydrobenzo[b]pyrans Using MMWCNTs-PEG-IL as a Novel Magnetic Immobilized Ionic Liquid

Abstract

Introduction: A novel immobilized imidazolium type ionic liquid was synthesized using poly(ethylene glycol) (PEG) functionalized magnetic multi-walled carbon nanotubes. This immobilized ionic liquid (MMWCNTs-PEG-IL) was characterized by FT-IR, VSM, XRD, FE-SEM and EDX analysis. Method: Then, it was used as a magnetic catalyst in a three-component reaction to yield tetrahydrobenzo[b]pyran derivatives. First, optimized reaction conditions were investigated. A mixture of containing dimedone (1 mmol), malononitrile (1 mmol), benzaldehyde (1.2 mmol) and MMWCNTs-PEG-IL (0.03 g) in H2O/EtOH (5 mL) was stirred at 70 °C. After completion of the reaction, the mixture was cooled. Results: Then, an external magnet was used to separate the magnetic catalyst. This method has many advantages including high reaction yields, high TOFs, using non-toxic solvents, easy handling of catalyst, simple separation of catalyst from reaction medium and short reaction times. Conclusion: Also, the reusability of the magnetic catalyst has been investigated in 7 runs without serious loss of reaction yield.