Montmorillonite-supported Reagents: A Powerful and Versatile Platform for the Synthesis of Biologically Active...

This review presents recent advances in montmorillonite-catalyzed organic transformations, highlighting its potential as an efficient, economical and environmentally benign solid-acid catalyst. Montmorillonite and its modified forms effectively promote a wide range of organic reactions, including multicomponent reactions, selective nitration, oxidation and reduction processes, and the synthesis of enamines, pyrroles, and β-lactams. Furthermore, integration with sustainable synthetic approaches such as microwave irradiation, ultrasound-assisted reactions, and solvent-free conditions further enhances reaction rates, improves conversions and selectivities, reduces the formation of undesirable by-products, while limiting the use of hazardous solvents. Particular emphasis is placed on hybrid catalytic systems in which metal salts, such as Bi(NO3)3 and SmI2, are supported on montmorillonite to improve catalytic activity, regioselectivity, and stereoselectivity. These methodologies demonstrate broad synthetic applicability for the preparation of pharmaceutically important compounds, including 1,4-dihydropyridines, β-lactams, aromatic amines, and nitrated derivatives of bioactive molecules such as eugenol and estradiol. Furthermore, a comparative evaluation of catalytic performance and the structural and spectroscopic characteristics of montmorillonite-based materials is also presented. Overall, montmorillonite-supported catalytic systems offer a versatile, efficient, and sustainable platform for advancing environmentally responsible organic synthesis.