Sulfated polyborate as Bronsted acid catalyst for Knoevenagel condensation

We have developed the use of Bronsted acid for Knoevenagel condensation. Sulfated polyborate has been used for efficient Knoevenagel condensation of aromatic, heterocyclic, α,β-unsaturated, and aliphatic aldehydes in the ecologically friendly ethanol: water (1:1) mixture as solvent at 70 °C. It took less time for certain aldehydes to react with active methylenes. The present method demonstrated significant benefits in terms of first-time use of Bronsted acid catalyst, mild reaction conditions, and better product yields.