Simple, Efficient, and Green Method for Synthesis of Trisubstituted Electrophilic Alkenes Using Lipase as a Biocatalyst

Abstract

A simple and efficient Knoevenagel condensation method for the synthesis of trisubstituted electrophilic alkenes was developed using lipase as a biocatalyst. Knoevenagel condensation was performed using the conventional method and using lipases (Aspergillus oryzae or Rhizopus oryzae) as biocatalysts, and reaction time, reaction temperature, yield, and recyclability were compared. Using a lipase as a biocatalyst eliminated the need for bases such as piperidine and pyridine. A wide range of aromatic aldehydes and ketones readily undergo condensation with active methylene compounds. The workup procedure is also very simple, and yields of the reactions are in the range of 75% to 95%. Both the biocatalysts were effectively recycled four times with no major decrease in the yield of product. The remarkable catalytic activity and reusability of lipase widens its applicability in Knoevenagel condensation with good to excellent yields for synthesis of trisubstituted electrophilic alkenes.

GRAPHICAL ABSTRACT

Keywords:

• Aromatic aldehyde
• biocatalyst
• Knoevenagel condensation
• lipase

ACKNOWLEDGMENT

The authors express their thanks to the University Grants Commission, New Delhi, India, for the financial support.

Notes

Note. Reaction conditions: N,N-dimethyl benzaldehyde (4.71 mmol), ethyl cyanoacetate (4.95 mmol), lipase (0.07 g), and solvent (5 ml) at 55 °C.

^a Isolated yields.

^b Reflux temperature.

Note. The products were characterized by FTIR, mass, ¹H NMR, and C, H, N analysis.

^a Isolated yield by conventional Knoevenagel condensation in ethanol at reflux.

^b Isolated yield by Aspergillus oryzae lipase.

^c Isolated yield by Rhizopus oryzae lipase.

Note. Reaction conditions: para-N,N-dimethyl benzaldehyde (4.71 mmol), ethyl cyanoacetate (4.95 mmol), lipase (0.07 g), and ethanol (5 ml) at 55°C for 6 h.

^a Isolated yields.