Simple Protocol for the Knoevenagel Condensation Under SolventFree Conditions using Tungstophosphoric Acid as Catalyst

The effect of calcination on the performance of tungstophosphoric acid for the product of Knoevenagel condensation was investigated. Substituted aldehydes and dimedone has been used in the presence of calcined tungstophosphoric acid as a heterogeneous catalyst using grinding method at room temperature. The results of reactions revealed that calcined tungstophosphoric acid has superior catalytic activity comparing to non-calcined catalyst in terms of yield and reaction time. Maximum yield of model compound was achieved by using 10 mol% of calcined catalyst in a reaction time that does not exceed10 min, whereas the yield at same amount of non-calcined catalyst was 86 % in a reaction time of 35 min.