Heteropolyacid-alumina composites as heterogeneous catalysts for the synthesis of organic compounds: a comprehensive review

Abstract

Heteropolyacids (HPAs) are well known for their application as catalysts in organic synthesis owing to their oxidizing capabilities and strong Brönsted acidity. However, a notable drawback of HPAs is their solubility in various reaction media, which has prompted the development of strategies to convert them into heterogeneous catalysts through immobilization on diverse materials. This review aims to describe recent advancements in the utilization of alumina as a support for HPAs and their applications as heterogeneous catalysts in the synthesis of organic compounds. Various strategies, methodologies, loading techniques, and the nature of HPAs, along with their acid and redox properties, are analyzed and compared. Several organic reactions, including oxidation processes, esterification, and the condensation synthesis of heterocycles, such as chromones and pyrroles, are explored.