Synthesis of novel pyrazolylbiscoumarin derivatives using FeTUD-1 as a mesoporous solid acid catalyst

Abstract

A series of novel pyrazolyl biscoumarins was synthesized at 80 °C in a one pot procedure using an Fe³⁺ incorporated mesoporous silicate catalyst (FeTUD-1). The wormhole structured FeTUD-1 catalyzed the condensation of pyrazole aldehyde (1,3-diphenyl-1H-pyrazole-4-carbaldehyde) and 4-hydroxy coumarin to give the product in ∼85% yield. XRD and N₂ sorption studies of FeTUD-1 confirmed its amorphous, mesoporous nature, which possessed a large surface area of 638 m² g⁻¹ and a pore diameter of 9.4 nm. The nature of Fe³⁺ ion co-ordination within the silica matrix was evaluated by different techniques including diffuse reflectance UV-Vis, FTIR, and EPR. FeTUD-1 possessed both Brønsted and Lewis acidity, as measured by FTIR of pyridine adsorption, that are responsible for the observed activities.