Novel Basic Ionic Liquid Based on Alkylammonium as Efficient Catalyst for Knoevenagel Reaction

Abstract

The typical Knoevenagel condensation was carried out smoothly in the presence of a basic ionic liquid of N,N,N′,N′-tetramethyl-N′-hexyl-ethylenediammonium tetrafluoroborate ([TMHEDA]BF₄), and 99% of yield was obtained using ethyl cyanoacetate and benzaldehyde as substrates at 60 °C for 1 h. Four reuses of the ionic liquid without dramatic decrease in catalytic activity for Knoevenagel condensation demonstrated the good stability and operability of the ionic liquid. Moreover, the typical nucleophilic addition reactions were also accomplished by the same ionic liquid to check its feasibility. The dual function of the basic ionic liquid both as solvent and catalyst, combined with simple product separation and recycling, is expected to contribute to the development of a green and environmentally friendly strategy.

GRAPHICAL ABSTRACT

Keywords:

• Basic ionic liquid
• dual function
• Knoevenagel condensation
• tetramethylethylenediamine

ACKNOWLEDGMENTS

The authors are grateful for financial support from the National Natural Science Foundation of China (31170556), Fundamental Research Funds for the Central Universities (YX2011-36, TD2011-11), Research Fund for the Doctoral Program of Higher Education of China (20100014120007), China Postdoctoral Science Foundation (20110490303), Beijing Forestry University Young Scientist Fund (BLX2009003), Major State Basic Research Development Program of China (973 Program, No. 2010CB732204), and China Ministry of Education (No. 111 project).

Notes

^a [TMHEDA]BF₄ (2.0 g), aldehyde or ketone (0.1 mol), and ethyl cyanoacetate (0.1 mol).

^b GC yield, conversion based on ethyl cyanoacetate.

^c Ionic liquid reused for the fourth time.

^a Reaction conditions: [TMHEDA]BF₄, 20 wt%; equivalent amount of two substrates; room temperature.

^b GC yield.

^c Five times excess of H₂O₂ to mesityl oxide.