Synthesis and Characterization of Nano Silica Supported Tungstophosphoric Acid: An Efficient, Reusable Heterogeneous Catalyst for the Synthesis of Azlactones

A rapid and scale up protocol for the synthesis of azlactones by the Erlenmeyer method under solvent-free conditions was developed. Tungstophosphoric acid supported on nano-silica, TPA@nano-SiO₂ was used as a heterogeneous catalyst for the synthesis of a wide range of azlactone derivatives. The catalyst was characterized by physicochemical measurements. The procedure was simple and permitted the quantitative isolation of products and catalyst under thermal conditions. The recycled catalyst was reused more than 5-times without loss of catalytic activity.