Preparation and properties of amorphous Cr/Fe mixed-aluminophosphates and their catalytic application in one pot-three component synthesis of 3,4- dihydropyrimidinones by Biginelli reaction

Hamza A. and Nagaraju N

Abstract

Amorphous aluminophosphate, Cr or Fe–aluminophosphates (2.5mol% of Cr or Fe) and Cr and Fealuminophosphates (2.5, 5 or 25 mol% of Cr and Fe) are prepared by co-precipitation method. These materials are characterized for their bulk, surface and acidic properties and applied as catalyst for the synthesis of biologically important 3,4-dihydropyramidinones by the Biginelli condensation of benzaldehyde, urea and ethylacetoacetate at ambient reaction conditions.The materials are found to be mesoporous, amorphous and possess high surface area and weak and strong acid sites depending on the type and concentration of the transition metals. All the materials are catalytically active with 100% selectivity towards the formation of Biginelli product. Among allthe catalysts, CrFeAlP with 5 mol % of Cr and Fe is found to be the best catalyst because of its higher concentration of weak acid sites and also higher surface area and porosity compared to other phosphate materials investigated. The material also found to be recyclable up to five cycles without losing catalytic activity significantly.