8-Amino-5,6,7,8-Tetrahydroquinolines as Ligands in Iridium(III) Catalysts for the Reduction of Aryl Ketones by asymmetric transfer hydrogenation (ATH)

Recently, it has been demonstrated the possibility to use iridium complexes as a valid alternative to the use of classical ruthenium systems.1 Aqua iridium(III) complexes with 8-amino-5,6,7,8- tetrahydroquinolines, CAMPY L1 and its derivatives as chiral ligands proved to be very efficient catalysts in the reduction of a wide range of prochiral aryl ketones, revealing a variety of behaviours in terms of reaction rate and stereoselectivity. Screening was carried out for the reduction of different types of aryl ketones and three hydrogen donors were evaluated: A deep variety of behaviours emerged by changing reaction conditions, stressing the matching between the substrates and the ligands used in the metal complexes. In particular the presence of HCOOH as hydrogen donor played an important role on the stereoselctivity of the catalysts. ATH reactions on β-lactam precursors led to interesting results achieving very high.