Hydrotalcites in organic synthesis: Multicomponent reactions

Abstract

Background: The use of solid bases as heterogeneous catalysts allows the replacement of conventional bases in Organic Chemistry, being of outmost importance. Lamellar double hydroxides or hydrotalcites are materials having excellent basic properties and high surface areas. As their surface properties have been used as bifunctional catalysts allowing the incorporation of metals and depending on the calcination temperature, these materials may exhibit Lewis or Brönsted basic sites. Additionally, they are widely used in various organic synthesis reactions. Objective: This contribution has been aimed to provide a compilation of the application of hydrotalcites as basic materials in organic synthesis, with a particular emphasis on multicomponent reactions. Conclusion: Hydrotalcites act as heterogeneous catalysts that conduct highly efficient processes in short reaction times and with the advantage of their easy recovery and reuse without significant loss of their catalytic activity. In addition, due to the modification of their structural and chemical properties, they are catalysts with multiple applications in organic synthesis such as Michael addition reactions, dehydrogenation reactions of alcohols, Knoevenagel condensations, reduction reactions, oxidations, epoxidations, multicomponent reactions, among others. Multicomponent reactions are of major interest since they allow obtaining compounds that have high biological activity and are generated through processes in a single step by combining three or more starting reagents under solvent-free conditions.