1-Substituted-imidazo[1,5-a]pyridin-3-ylidenes as Highly Efficient Ligands for Rh- and Ir-catalyzed Transfer Hydrogenation of Carbonyl Compounds

The transfer hydrogenation of carbonyl compounds catalyzed by Rh and Ir complexes bearing 1-substituted-imidazo[1,5-a]pyridin-3-ylidene ligands is reported. These catalysts, especially the Rh catalyst, showed high efficiency for the reaction. Comparison of the reaction profiles of several conventional Rh-NHC and -phosphine complexes with the present system revealed that the present catalytic system offers several advantages, and clearly showed greater efficiency than the other systems.