A library approach to the development of chiral supramolecular ligands for asymmetric hydrogenation

The creation of chiral ligands of simple structure and truly easy preparation is the condition for supramolecular catalysis to become of practical industrial use. To this end, we developed a library of chiral monodentate phosphites, named BenzaPhos,[1] which can be prepared in only two simple steps from readily available compounds. The new ligands, containing a benzoic acid primary amide group capable of hydrogen bonding interactions, showed excellent activity and stereocontrol in the enantioselective hydrogenation of both benchmark substrates and ‘challenging’ olefins. A series of experiments and computational studies strongly suggest that ligand-substrate H-bonding crucially affects these outstanding catalytic properties. [1] L. Pignataro, C. Bovio, M. Civera, U. Piarulli, C. Gennari, Chem. Eur. J. 2012, 18, DOI: 10.1002/chem.201201032.