2-Methyltetrahydrofuran: A Green Solvent for Iron-Catalyzed Cross-Coupling Reactions

Iron-catalyzed cross-coupling reactions allow sustainable formation of C-C bonds using cost-effective, earth-abundant base-metal catalysis for complex syntheses of pharmaceuticals, natural products, and fine chemicals. The major challenge to maintain full sustainability of the process is the identification of green and renewable solvents that can be harnessed to replace the conventional solvents for this highly attractive reaction. Herein, iron-catalyzed cross-coupling of aryl chlorides and tosylates with challenging organometallic reagents possessing β-hydrogens is found to proceed in good to excellent yields with the green, sustainable, and eco-friendly 2-methyltetrahydrofuran (2-MeTHF) as solvent. The reaction operates with excellent functional group tolerance under very mild conditions. Furthermore, large-scale cross-coupling, cross-coupling of heteroaromatic substrates, and cross-coupling of challenging aryl tosylates and carbamates mediated by Fe-N-heterocyclic carbene catalytic systems in eco-friendly 2-MeTHF were also carried out. The developed method was applied to the key cross-coupling in the synthesis of a fibrinolysis inhibitor, further highlighting the potential of 2-MeTHF as a general solvent for sustainable iron-catalyzed cross-coupling reactions.