A solvent free approach for Knoevenagel condensation: Facile synthesis of 3-cyano and 3-carbethoxycoumarins

Abstract

A simple, efficient and solvent free approach for the Knoevenagel condensation has been developed which involves grinding of active methylene compounds with aromatic aldehydes over basic alumina. Using this solvent free Knoevenagel approach, a facile and efficient synthesis of 3-cyano and 3-carbethoxycoumarins has also been developed, which involves the grinding of 2-hydroxybenzaldehydes with malononitrile or ethylcyanoacetate respectively over basic alumina followed by grinding with p-toluenesulphonic acid (PTSA) in the same mortar.