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

Abstract

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 exceed 10 min, whereas the yield at same amount of non-calcined catalyst was 86 % in a reaction time of 35 min.

Pd-HPW/SiO2 Bi-Functional Catalyst: Sonochemical Synthesis, Characterization, and Effect on Octahydroquinazolinone Synthesis

“…The peak at 792 and 796 cm −1 corresponded to the corner sharing band of W-O-W. This suggests that, regardless of the preparation process, the HPW retained the Keggin structure, which was already confirmed by our previous efforts [42,43] .The peak assigned at 1066 and 1077 cm −1 may have been due to Si-O-Si stretching vibrations [42]. Some other peaks for SiO and SiO2 may not have been visible due to the overlapping of HPW as result of impregnation with the SiO2 support [42].…”