Bis(azolium)dichloride salts constitute stable and convenient precursors of metal bis(carbenes) as ligands for metal-catalyzed processes such as cross-coupling reactions. However, the synthesis of these salts is inefficient in part due to the low reactivity of alkyl chloride in nucleophilic substitution reactions. New reaction kinetics and mechanistic studies on pyridine derivatives in the literature prompted us to develop a novel method for the improved synthesis of bis(azolium) dichloride salts in excellent yields, applicable to a wide scope of heterocyclic cores. Known limitations of the reaction, specifically in accessing methylene-bridged bis(azolium) salts, were addressed by using an excess of CH2Cl2 and a cosolvent, DMSO, which improves conversion by stabilizing the SN2 transition state. Applications of this method include the direct synthesis of various metal bis(carbenes) in one-pot reactions directly from imidazole derivatives, exemplified by the formation of palladium-, silver-, and gold-bis(NHC) complexes.

Simple and expedient synthesis of bis(azolium)dichloride salts from dichloroalkanes and imidazoles

ACS Spring Meeting 2021

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.