Mechanochemistry to Form Substituted Imidazoles, Imidazolium Salts and NHC-Gold Complexes with Fluorine-Containing...

Synthesis of organometallic compounds has had an enormous impact on medicine. In this context, gold complexes are gaining much interest since the discovery of the cytotoxic effect of cisplatin. On the other hand, in the last two decades, the mechanochemical synthetic approaches have been developed considerably demonstrating that they could also be a powerful tool enabling environmentally benign and sustainable synthesis of metal complexes. The present work focuses on mechanochemical synthesis of precursors and gold-NHC complexes of type NHCAuCl and [AubisNHC]⁺. The mechanochemical approach has been studied to afford four substituted imidazoles, eight imidazolium salts and six NHCAuCl and one [AubisNHC]⁺. Substituted imidazoles were obtained with yields varying between 29-99%. Five imidazolium salts bearing aliphatic carbon atoms were obtained, with yields from 46-81%. It is important to notice that the reaction can follow the aging process giving rise to imidazolium salts in very good yields. Concerning the gold(I) complexes, for the first time, six mono NHC complexes of type NHCAuCl have been synthesized, five of them with yields varying between 41-83%. Finally, compound 19 [AubisNHC]⁺ has been obtained not only by transmetallation, but most gratifyingly through direct metalation in 73% yield.