A pyrazole ligand improves the efficiency of Mn-catalysts for transfer hydrogenation†

Abstract

The high cost associated with noble metal catalysts has led to a surge in interest towards harnessing the abundant 3D metals as catalysts for catalytic hydrogenation. Many 3D metal catalysts have been disclosed in recent years for transfer hydrogenation reactions, but the reported catalyst metal loads are too high compared to precious metal catalysts, sometimes up to three orders of magnitude higher. Therefore, it is necessary to solve the actual coordination of ligands and metals in non-precious metal catalysts and avoid excessive consumption of transition metals and ligands, in order to realize the effective practical application of 3D metal catalytic systems in various industries. A practical and scalable catalytic system employing pyrazole ligands coordinated to Mn is introduced for transfer hydrogenations. By means of pre-activation via dehydrohalogenation, an efficient and unprecedented Mn–N₂ catalytic system has been established, showcasing exceptional tolerance towards a diverse array of functional groups and enabling broad application across a wide range of alcohols. Significantly, this protocol facilitates the facile synthesis of multiple pharmaceuticals within a single reaction vessel.