0940 - 1020 Andreas Pfaltz

Iridium-Catalyzed Asymmetric Hydrogenation 

For a long time, C₂-symmetric ligands have been dominating in asymmetric catalysis. However, more recently it was found that in a number of metal-catalyzed processes non-symmetric mixed-donor bidentate P,N-ligands are superior to C₂-symmetric P,P- or N,N-ligands. Especially phosphino­oxazolines (PHOX ligands) have proven to be highly versatile, very effective ligands in many enantioselective catalytic reactions, including hydrogenation of C=N and C=C bonds, Heck reactions, allylic substitutions and conjugate addition to enones [1].  

We have found that iridium complexes with PHOX or other chiral P,N-ligands such as 2 and 3  are efficient catalysts for the asymmetric hydrogenation of olefins [2]. These catalysts are readily prepared, air-stable and easy to handle. In contrast to rhodium- and ruthenium-phosphine complexes, they do not require the presence of a coordinating group next to the C=C bond and, therefore, considerably expand the application range of asymmetric hydrogenation. In this lecture, the special properties, the scope and recent applications of these catalysts will be discussed.