Mechanochemical activation of NHC–CS2 adducts for the generation of N-heterocyclic carbenes

Abstract

Stable N-heterocyclic carbenes (NHCs) have garnered significant attention in synthetic chemistry due to their versatile applications. In this study, we explored a novel mechanochemical method for the generation of free carbenes, which could be a good complement to traditional approaches that require strong bases or reductants. Ball milling of NHC–CS₂ adducts at room temperature successfully resulted in the quantitative formation of free carbenes that can be subsequently trapped by sulfur or selenium. Importantly, heating NHC–CS₂ adducts in solution phase did not lead to the successful generation of free carbenes, in agreement with the high activation energy required for NHC–CS₂ dissociation. These findings underscore the potential of ball milling as a robust and versatile approach for generating NHCs from stable NHC-small molecule adducts, and opens new avenues for developing mechanochemical strategies for generating valuable NHC-derived compounds.