Ball-mill-assisted mechanochemical approaches for heterocyclic compound synthesis (2015-2024)

Ball milling has emerged as a powerful and sustainable technique for the synthesis of heterocyclic compounds, offering significant advantages over conventional methods. This review explores recent advancements in the application of ball milling for environmentally friendly synthesis, highlighting its role in accelerating reaction times, enhancing yields, and minimizing solvent usage. Various studies have demonstrated its efficacy in synthesizing diverse nitrogen, oxygen, and sulfur-containing heterocyclic frameworks, including benzoxazines, quinoxalines, pyrazolothienopyrimidines, chalcones, spiro(indole-pyrrolidine) derivatives, quinolines, pyridazines, triazolochromenes, arylsulfonyl 4H-pyrans, aminothiophenes, methylcoumarins, and benzothiazoles. Notably, high-energy and planetary ball milling have facilitated key transformations such as hydroamination, Knoevenagel condensation, and reductive reactions, often yielding products with excellent enantiomeric purity while eliminating the need for chromatographic purification. Despite its advantages, challenges like scalability, reaction monitoring, and equipment wear persist. Innovations in reactor design, monitoring techniques, and computational modeling can enhance the application of ball mill in green chemistry. By providing a comprehensive analysis of reaction mechanisms and sustainability aspects, this review underscores the potential of mechanochemical synthesis to redefine heterocyclic chemistry and drive advancements in pharmaceuticals, agrochemicals, and materials science.