Background:
The Knoevenagel condensation is an important reaction in organic chemistry
because of its capacity to form new C-C bonds and its products are mainly used in organic synthesis as
intermediates, due to the large number of reactions they can undergo. Based on the importance of the
Knoevenagel adducts, a sustainable synthetic methodology was developed employing microwave irradiation.
Objective:
Develop a synthetic methodology employing microwave irradiation and green solvents to
obtain Knoevenagel adducts with high yields.
Methods:
Knoevenagel condensation reactions were evaluated with different basic catalysts, as well as
in the presence or absence of microwave irradiation. The scope of the reaction was expanded using
different aldehydes, cyanoacetamide or methyl cyanoacetate. The geometry of the formed products
was also evaluated.
Results:
After the optimization process, the reactions between aldehydes and cyanoacetamide were
performed with triethylamine as catalyst, in the presence of microwave irradiation, in 35 minutes, using
NaCl solution as solvent and resulted in high yields 90-99%. The reactions performed between
aldehydes and methyl cyanoacetate were also performed under these conditions, but showed better
yields with EtOH as solvent 70-90%. Finally, from X-ray analysis, the (E)-geometry of these compounds
was confirmed.
Conclusion:
In this study we developed synthetic methodology of Knoevenagel condensation using
triethylamine, green solvents and microwave irradiation. In 35 minutes, products with high yields (70-
99%) were obtained and the (E)-geometry of the adducts was confirmed.
Review: Microwave-Promoted Organic Synthesis
