Anhydrous copper sulfate-assisted Knoevenagel condensation under neutral conditions

Anhydrous copper sulfate is identified as a promoter for Knoevenagel condensation with surprising activity and excellent isolated yields. Low cost, easy availability and convenient to handle anhydrous copper sulfate was used to enhance the Knoevenagel condensation reaction by acting as a strong dehydrating agent. The developed protocol demonstrated high efficiency in condensation of Aryl aldehydes with activated methylene compounds like malononitrile and ethyl cyanoacetate under mild reaction condition. To ensure general applicability, differently substituted aromatic aldehydes were condensed with malononitrile and ethyl-2-cyanoacetate affording corresponding products in excellent yield. A recycling test revealed that the heterogeneous dehydrating agent could be reused without experiencing a significant loss of activity. It is easily recovered by filtration and recycled efficiently. Graphical abstract