Ambient-Pressure and Base-Free Aldehyde Hydrogenation Catalyst Supported by a Bifunctional Abnormal NHC Ligand

Catalytic aldehyde hydrogenation is an essential and routinely used chemical synthesis process in both academia and industry. However, there is a serious scarcity of efficient homogeneous catalysts for this process to work under highly demanding atmospheric-pressure, base-free, and aqueous conditions. Addressing this problem, herein, we report an iridium-based catalyst for facile atmospheric-pressure and base-free hydrogenation of various aromatic, heteroaromatic, and aliphatic aldehydes. The catalyst also displays excellent chemoselectivity toward aldehyde over other carbonyl functionalities and unsaturated motifs. Moreover, the catalyst is found to work in H2O (and in H2O-ethanol) medium at ambient temperature. All of the above attributes have been possible to incorporate into this unique catalyst via employing a hybrid bifunctional ligand, which plays a crucial role in facilitating the cleavage of H-2 as well as effectively delivering hydride to substrate without any help of base or pressure.