Synthesis of chiral P,S ferrocenyl ligands for catalyst heterogenization and testing in the homogeneous asymmetric hydrogenation of acetophenone

• Development of ferrocenyl P,S ligands suitable for grafting to a silica surface • The ether tether introduced for future grafting does not alter catalyst performance • Activity and ee are negatively affected by increased base for the in-situ catalyst • The base promotes activity and has no effect on ee for the pre-made catalyst Racemic and chiral P,S ferrocenyl ligands bearing a phenol function for further catalyst grafting were synthesized and fully characterized (multinuclear NMR, high-resolution MS, X-ray diffraction). Analogs bearing a methoxy group instead of OH (anisole instead of phenol) were also synthesized to mimic the expected ether formation after grafting in order to assess the ether group influence on catalysis. Good activity and enantioselectivity (up to 78%), similar to non-functionalized ligands, were obtained in the asymmetric hydrogenation of acetophenone. The base concentration appears to have major influence on both activity and enantioselectivity.