Synthesis of a New Class of Chiral 1,5-Diphosphanylferrocene Ligands and Their Use in Enantioselective Hydrogenation

A new family of ferrocenylphosphane ligands has been prepared. Their flexible synthesis allows many structural modifications. The asymmetric induction of these ligands was examined in the hydrogenation of functionalized C=C, C=O, and C=N bonds. The enantioselectivity of the reaction was strongly dependent on the substituent R at the position α to the ferrocene moiety. In many cases, both enantiomeric β‐hydroxyesters of the reduction product can be obtained by simply replacing a dimethylamino group in the ligand with a methyl group. The highly flexible synthesis of the new family of ferrocenyl phosphane ligands 1 offers many possibilities for variation of their substituents. The structure of 1 can thus be rapidly modified to optimize ligand–substrate matching. Ligands 1 give excellent enantioselectivities in the metal‐catalyzed hydrogenation of functionalized C=C, C=O, and C=N bonds and 1,3‐dicarbonyl compounds. Furthermore, both configurations of the reduction products could be obtained by merely modifying the substituent in the position α to the ferrocene moiety.