Sodium Benzoate as a Green, Efficient, and Recyclable Catalyst for Knoevenagel Condensation

Abstract

Sodium benzoate was utilized as a novel efficient and green catalyst for the Knoevenagel condensation of aldehydes with active methylene compounds such as ethyl cyanoacetate and malononitrile to afford substituted olefins through the conventional stirring or under ultrasounic irradiation. Improvements were observed by carrying out the reactions under ultrasound irradiation. The reaction proceeded smoothly under mild conditions at room temperature, and the products were obtained in excellent yields within short times: The catalyst remains active and exhibits no substantial loss of activity for up to four reaction cycles.

GRAPHICAL ABSTRACT

Keywords:

• Catalysis
• Knoevenagel
• sodium benzoate
• ultrasound irradiation

ACKNOWLEDGMENTS

This work was supported by Shandong Province Natural Science Foundation (ZR2010BL017). We gratefully thank Prof. Heng Jiang for his kind help and Taishan University for financial support.

Notes

^a Isolated yield.

^a The reaction was carried out in 2 mL of solvent.

^b Isolated yield.

^a A, without ultrasound irradiation.

^b B, under ultrasound irradiation.

^c Isolated yield.

^d Under ultrasound irradiation in 2 mL C₂H₅OH.

^a Isolated yield.

^a Isolated yield.

^b Under ultrasound irradiation.