Iron-Promoted Kumada Cross-Couplings in Deep Eutectic Solvents Under Mild Conditions

Over the past decades, iron-catalyzed Kumada-type cross-couplings have undergone considerable refinement, especially in the context of Csp³ alkyl halides reacting with Csp² aryl Grignard reagents. These transformations are classically performed in anhydrous THF, under inert atmosphere, and typically rely on additives such as TMEDA to promote efficient catalyst performance. Recognising both the potential of organolithium and Grignard reagents in deep eutectic solvents (DESs)and building on our previous work on fast palladium-catalyzed cross-couplings of organolithium and organozinc reagents in greener media, we embarked on an ambitious study to investigate the reactivity of these organometallic species in DESs under iron catalysis and aerobic conditions at room temperature, aiming to develop a more sustainable methodology for such transformations. In this communication, we report preliminary results obtained using DESs as the reaction medium. These findings suggest that ligands such as TMEDA may lose their effectiveness under heterogeneous conditions– unlike in homogeneous systems–withing strongly hydrogen-bonded media, and that DES environment may play a crucial role in suppressing homocoupling by-product formation, while preventing the immediate quenching of the organometallic species.