Role of Copper in Mechanochemical C‐H activation Approaches: Mechanochemistry in C‐C, C‐X Bonds Formation

Mechanochemistry, an alternative eco‐friendly approach towards the synthesis of organic compounds under solvent‐free conditions, is an attractive emerging area of research in chemistry. In this process, the chemical reactions are activated directly or indirectly by applying mechanical forces. Further reaction improvements can be made by choosing a specific material for the milling vials and balls used for the mechanochemical process. Herein, we have summarised the literature work published by the researchers on the role of copper metal in high‐energy ball milling processes. The copper acts as a catalyst in the form of copper compounds, such as Cu(II)‐pybo, Cu(OAc)2, Cu(OTf)2, etc., or in the form of copper balls or copper vials. Chlorination of aromatic hydrocarbons, multicomponent reactions, cycloadditions, atom transfer radical cyclizations, cross‐coupling reactions such as Sonogashira coupling, aldehyde‐alkyne‐amine (A3) coupling, Glaser coupling, asymmetric cross‐dehydrogenative‐coupling (CDC), etc., were successfully proceeded mechanochemically, resulting in moderate to good yield of the desired products. Even drugs like tolbutamide, chlorpropamide, etc., were synthesized successfully by employing this methodology, highlighting its importance in pharmaceutical industries.