Lewis Acid-Promoted Heterogeneous Platinum Catalysts for Hydrogenation of Amides to Amines

For the hydrogenation of a tertiary amide (N-acetylpiperidine), Lewis acidic support materials (Nb2O5 and MoOx/TiO2) increase the catalytic activity of Pt metal nanoparticles by a factor of > 100. In situ infrared (IR) study shows that coordination of the C=O group of amide to surface Lewis acid sites weakens the C=O bond, and the activated amide undergoes hydrogen transfer from H species on Pt sites. Among 19 types of heterogeneous catalysts tested, Pt/Nb2O5 shows the highest catalytic activity. Pt/Nb2O5 is generally effective for the selective hydrogenation of various tertiary amides and e-caprolactam to the corresponding amines under additive-free and solventless conditions and shows an order of higher turnover number (TON) than previously reported catalysts. Pt-MoOx/TiO2 is the secondary most effective and is reusable 10 times after the reaction.