The Key Role of the Hemiaminal Intermediate in the Iron-Catalyzed Deaminative Hydrogenation of Amides

Abstract

Amides functionalities are among the most widely found groups in biologically active molecules, and their selective catalytic reduction is an important target for synthetic methods. Recent advances in base metal catalysis have identified efficient systems for selective hydrogenolysis of the amide C–N linkage. This study examines in detail the mechanism for deaminative hydrogenation of formanilide and dimethylformamide (DMF) to the corresponding amines (aniline and dimethylamine, respectively) and methanol catalyzed by (iPrPNHP)Fe(H)2(CO) (iPrPNHP = HN{CH2CH2(PiPr2)}2) using density functional theory (DFT) calculations and microkinetic modeling. Following an initial hydrogenation of the amide carbonyl group, protonolysis of the C–N bond of the hemiaminal intermediate produces amine and formaldehyde, which is further hydrogenated to methanol. Remarkably, protonolysis of the C–N bond of the hemiaminal intermediate follows different pathways, depending on the nature of the substrate and the experimental condi...