Chiral Isonitriles-Iron-Cyclopentadienone Complexes for Enantioselective Transfer Hydrogenation of Ketones

Overview & Synopsis

By substituting one CO ligand with an isonitrile, we have developed a novel class of chiral iron cyclopentadienone complexes that are active in transfer hydrogenation under photoactivation. These complexes display high reactivity across a broad range of substrates, achieving enantiomeric ratios of up to 78:22. We explored various strategies for introducing chirality into the iron complex, including the use of chiral cyclopentadienone ligands, chiral isonitrile ligands, and combinations of both. Upon light irradiation, CO dissociation renders the iron center stereogenic, resulting in unique chiral molecules with multiple stereogenic elements. Notably, these iron complexes efficiently reduce ketones under mild conditions using isopropanol as a hydrogen donor, eliminating the need for high hydrogen pressures typically required for such systems. Insights into the role of the chiral cyclopentadienone ligand offer promising directions for designing more selective chiral iron catalysts.