Knölker Iron Catalysts for Hydrogenation Revisited: A Nonspectator Solvent and Fine-Tuning

Abstract

The reductive amination process under hydrogen at high pressure catalyzed by iron complexes is of great synthetic interest. In this work, we report density functional theory (DFT) studies on the reductive amination catalyzed by a Knölker-type iron complex. Different modifications of the catalyst are explored to improve the efficiency and guide experiments toward milder conditions. DFT calculations in conjunction with analysis of the chemical structure in terms of geometry, fragment partial charges, effective oxidation states (EOS), and aromaticity allows us to conclude that the presence of electron-withdrawing substituents on the cyclopentadienone ring induces a decrease of the activation barriers of most relevant steps, leading to a more efficient catalysis. The present work is a clear example that predictive catalysis can have a fundamental role in sustainable catalytic transformations.