A retrospective 9-years overview of sulfated polyborate as a robust catalyst for organic transformations

Sulfated polyborate (SPB) is a homogeneous catalyst that showcases dual acidic properties of Brønsted and Lewis acid. The SPB catalyst is boron-centered, which makes it more sustainable as it inherits non-metallic and non-hazardous traits. SPB, a green and adaptable metal-free catalyst, is prepared from readily available boric acid, offering economic and environmental benefits. It is highly tolerable to functional groups due to its simple, facile, eco-friendly, and hassle-free isolation procedure, which establishes it as a versatile, promising, and flexible catalyst compared to metal-based catalysts. The general overview of SPB preparation is followed by its manifold applications in Betti-base synthesis, Kabachnik–Field reaction, Ritter reaction, Biginelli reaction, Kindler reaction, and various other organic transformations. The catalyst interacts with the reactant species to enhance the reaction rates. It follows a common reaction mechanism to frame products, specifically Knoevenagel condensation, followed by the Michael addition pathway. This review presents the preparation and characterization of SPB, followed by its various catalytic applications in organic synthesis over the past 9 years.