New Chiral P,N-Ferrocenyl Ligands Applied to Hydrogenation of Imines

Significance

The primary focus of this work is the synthesis of the new P,N-ligand class 4. Its utility was demonstrated through the asymmetric hydrogenation of acyclic imines. Although both dia­stereomers of ligands 4 and 5 can be prepared, the α-diastereomers (shown) gave better selectivity. Importantly, iridium complex 6 selectively reduced the imine precursor to 8 and left the pendant ketone untouched. Chiral pyrrolidinones and piperidinones can be prepared with this method. The cyclization occurs spontaneoulsy under the mild deprotection conditions.