A Mechanistic Perspective on the Mechanochemical Method To Reduce Carbonyl Groups with Stainless Steel and Water

Mechanochemistry through high-speed ball milling has become an increasingly popular method for performing organic transformations. This newfound interest in high-speed ball milling is in part driven by the benefit of performing reactions in the absence of solvent. Mechanochemical reactions are often conducted in stainless-steel vials with stainless-steel balls. Since stainless steel is made of several readily oxidizable metals (Fe, Cr, and Ni), reduction reactions using water as a hydrogen source were explored using a temperature-controlled mixer mill. Mechanistic studies suggest that the reduction proceeds via a single electron transfer (SET) pathway, with iron and nickel being essential components for the reaction.