Asymmetric transfer hydrogenation of aromatic ketones with chiral diamino-thiophene/iridium catalyst systems

Abstract

The chiral diamino-bis(bithiophene) ligands were firstly employed in the iridium(I)-catalyzed asymmetric transfer hydrogenation of aromatic ketones. The new catalyst systems, generated in situ from chiral diamino-bis(bithiophene) ligands and IrCl(CO)(PPh 3) 2 in i PrOH, gave the corresponding optically active secondary alcohols with high yield and fair to good enantioselectivities (up to 90% ee). The chiral Ir(I)/diamino-bis(bithiophene) complexes were also synthesized and characterized. The XPS spectra showed that the potentially multidentate ligands coordinated to the Ir atom through the nitrogen atoms, while the thiophene pendants did not participate in coordination to the Ir atom.