ABSTRACT
Heterogeneous catalysis is a type of catalysis in which the catalyst and reactants are present in different phases. It provides an important avenue for the growth and development of sustainable science and technologies, and also highly efcient and eco-friendly synthetic protocols with minimal environmental impact. It involves the application of solid-supported reagents, preferably under solvent-free conditions. The use of reusable heterogeneous catalysts minimizes the consumption of auxiliary substances. It is useful in terms of saving energy and time and achieving separation, and has signicant economic and environmental benets. It assists in the development of safer, cleaner, and more economically feasible processes. There has been
5.1 Introduction .................................................................................................. 133 5.2 Preparation of Silica Sulfuric Acid............................................................... 135 5.3 Benets of Silica Sulfuric Acid Catalyst ...................................................... 135 5.4 Silica Sulfuric Acid-Catalyzed Reactions ................................................... 135
5.4.1 Synthesis of Heterocyclic Compounds ............................................. 136 5.4.1.1 Synthesis of Nitrogen-Containing Heterocyclic Compounds .... 136 5.4.1.2 Synthesis of Oxygen-Containing Heterocyclic Compounds ....144 5.4.1.3 Synthesis of Sulfur-Containing Heterocyclic Compounds .....146
