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High Chemoselectivity of an Advanced Iron Catalyst for the Hydrogenation of Aldehydes with Isolated CC Bond: A Computational Study

Lu, Xi, Cheng, Runjiao, Turner, Nicholas, Liu, Qian, Zhang, Mingtao, Sun, Xiaomin
Journal of organic chemistry 2014 v.79 no.19 pp. 9355-9364
Gibbs free energy, aldehydes, ambient temperature, catalysts, chemical structure, chemoselectivity, energy, hydrogen, hydrogenation, iron, methodology, olefin, organic chemistry, toxicity
Knölker’s iron complex is a “green” catalyst that exhibits low toxicity and is abundant in nature. Density functional theory (DFT) was used to explore the highly chemoselective nature of the catalytic hydrogenation of CH₂CHCH₂CHO. An outer-sphere concerted hydrogen transfer was found to be the most reasonable kinetic route for the hydrogenation of the olefin. However, the CC hydrogenation reaction has a high free energy barrier of 28.1 kcal/mol, requiring a high temperature to overcome. By comparison, the CHO bond concerted hydrogen-transfer reaction catalyzed using Knölker’s iron catalyst has an energy barrier of only 14.0 kcal/mol. Therefore, only the CHO of CH₂CHCH₂CHO can be hydrogenated in the presence of Knölker’s catalyst at room temperature, due to kinetic domination. All computational results were in good agreement with experimental results.