Advanced green synthesis: Solvent-free and catalyst-free reaction

The solvent-free and catalyst-free (SFCF) reaction has garnered significant interest among chemists due to its alignment with many of the 12 principles of green chemistry. In recent years, numerous innovative techniques have been employed to expand the scope of SFCF reactions and diversify the range of substrates. This paper presents an exhaustive examination of these transformations involving various functional groups, including alkenes, alkynes, aldehydes, ketones, imines, carboxylic acids, anhydrides, amides, amines, epoxides, aziridines, and organoselenides. Our review primarily seeks to elucidate the impact of solvent and concentration effects on these reactions by applying novel theories, such as the aggregate effect, multi-body effect, and multiple weak interactions, to ascertain how solvents impede these reactions. Additionally, different reaction mechanisms are contrasted under catalytic versus non-catalytic as well as solvent versus non-solvent conditions. Furthermore, the applications of such environmentally friendly reactions in fields such as material synthesis and drug synthesis are emphasized. This review provides a comprehensive overview of solvent-free and catalyst-free reactions. Theoretical foundations, energy supply methodologies, reaction classifications, substrate diversity, and practical applications of materials and medicine were highlighted.