Iron-Catalyzed Kumada Cross-Coupling In Deep Eutectic Solvents

Iron-catalyzed Grignard couplings (Kumada-type) have undergone substantial development over the past decades, particularly for the coupling of alkyl halides (Csp³) with aryl Grignard reagents (Csp²), typically employing TMEDA as an additive and anhydrous tetrahydrofuran (THF) as the preferred solvent under an inert atmosphere . Recognising both the potential of organolithium and Grignard reagents in deep eutectic solvents (DESs) and building on our previous work on fast palladiumcatalyzed 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.